Was in a world building mood and I'm once again judging Harry Potter's world-building. Setting aside its other narrative problems and the author's current actions for now - those are whole other cans of worms - the world-building is mostly vibes and aesthetics based, which isn't inherently bad, but in a franchise whose main hook is the wonder of a whole hidden world, the world-building should have been more substantial.

It doesn't even need a lot of reworking, just given more follow ups or wider impacts.

For example...

Lore: There are no electrical devices in the wizarding world.

Canon Reason
Electricity doesn't function in magical areas. Magic and technology do not mix.

(Likely) Meta Reasons

• Leaning into the vintage aesthetics.
• Makes it easier to plot, without the additional inconvenience of researching relevant technology.

Cooler Reasons

• It does work, but in high magic areas, the components of electrical devices start exhibiting magical properties that muggle creators did not account for. Wizarding electrical technology is behind as they need to keep track of more variables.
• Prejudice and propaganda. It was a muggle who first harnessed electricity. Due to strong prejudice, the wizarding world looked down on technological advancements, and treated those who used it or pushed for it with disdain and contempt.

Lore: Wizards write with quills and parchment paper.

Canon Reason
Wizards are quirky and behind the times.

(Likely) Meta Reasons
Cool wizard aesthetics.

Cooler Reasons

• Ink has magical properties...
  • ...so wizards are familiarized early on with various types of dip pens (not sure why these don't exist) and quills, which allow for more varieties of ink.
  • ...and metal interacts with the ink's properties, so quills are the writing tool of choice.
  • ...that is also affected by the writing tool. Feather quills are the most common (due to the bird mailing system) and versatile (color, bird species, feather type, etc.) tool, so wizards are taught how to use and maintain quill pens.
• Prejudice, again. Dip pens and other types of pens were invented by muggles, so it's considered a "lesser" writing tool.
• Big quill company has a monopoly on the writing tools and accessories industry, and is actively suppressing other products and companies.
• Writing tools are a class marker and status symbol. Quills are common and cheap because of the bird mailing system. Dip pens and fountain pens are considered luxury items for their durability, material, and aesthetic potential.

Lore: Hogwarts divides its students into four different houses based on their personality.

Canon Reasons
Dormitory naming theme.
The four founders of the school were divided on the traits they considered most important.

(Likely) Meta Reasons
Lazy characterization and political shortcut.
Flawed and lazy way to show "good" and "evil" factions.

Cooler Reason

It's a holdover from the apprenticeship style of education. The associated house traits were just whatever blended well with the founder's original profession before they banded together to form a school.

• Gryffindor: Likely an explorer, adventurer, or field researcher who took his students on his travels for hands-on work. His students needed to be brave and bold enough to travel to unknown lands, be open to new situations, and have good initiative to handle unexpected turns of events well on the fly.
• Slytherin: Probably a courtier or diplomat, someone who was always under public scrutiny. Anything he associated with were considered reflections of his character and competitiveness. And so he preferred those who were observant, tactful, and able to read between the lines and follow the threads of intrigue and personal history that moved people to act the way they did.
• Ravenclaw: Scribe, historian, or clergy - professions associated with intellect, literacy, and handling large volumes of information. Organizational skills required. Work could easily become tedious, so only those who are truly passionate about knowledge endured. As mistakes can accumulate quickly in this environment, incautious and unobservant students were usually removed from her tutelage.
• Hufflepuff: High ranking position charged with taking care of domestic affairs - like one of noble peerage. She handled foundational yet often underappreciated work, and ensured some level of working peace and civility between different groups of people - enough to to get everyone on track towards a larger goal, or just to coexist in one gathering for a few weeks. This required large amounts of patience, quiet but unshakeable strength, the ability to read a room and create acceptable and fair compromises, and form meaningful connections to different groups of people.

As the school changed heads several times along the ages and began to focus more on general education, the significance of the shared traits was lost, and the administrators wrongly assumed the reason behind it.

Lore: Time travel magic exists, and the government allowed a 13-year old to play with it.

Canon Reason
Academic overachiever impressed people so much, she was given special privileges so she could continue burning herself out.

(Likely) Meta Reasons
Author wanted to write a story with time travel in it.

Cooler Reasons

• Time magic is a normal, if advanced, type of magic, in the same way computers and programming are normal technologies now, but providing a 13-year old student admin-level access to her school's database is highly unusual and requires a lot of trust and responsibility.
• Time magic IS dangerous, unstable, and experimental. The ministry just considers Hermione a disposable test subject due to her lineage.
• Time magic IS dangerous, but in the same way cars are dangerous. Misuse of time magic can cause time-space ending paradoxes, but there's a lot of safety implements in place, so mishaps are generally minor and easy to fix. The usual punishment is a fine, and probably getting yelled at by overworked government employees who now have to fix what you broke.

The problem with adding something as cool as time travel in a story is that it's impossible to just put it down and forget about it. Time travel opens so many possibilities, from mind-bending paradoxes, direct access to historical events, and even alternate timelines to reject, regret, or strive towards.

The protagonists could personally experience events from the past - from the era of Tom Riddle, to the Mauraders, to Dumbledore's youth, the Hogwarts founders themselves - even interact with these people, learn about the context of their actions, their motivations, humanizing idols, heroes, and enemies alike. A change inflicted upon the past could end up becoming the key to their victory. Or they could be split up and be forced to live through different time periods, their experience changing and alienating them from their friends. They could face the heartbreak of knowing that there could have been a better future, if only they were more cautious, if only they were more selfish. They could play time travel hopscotch, weakening long-planned devastating ritual by compromising each component through the past.

Lore: House elves like being slaves.

Canon Reason
It's a culture thing.

(Likely) Meta Reasons

• The slavery allegory was only planned for one book. Author failed to properly consider the implications of such a lore, and the justifications to not pursue the story behind it.
• A handwaved explanation for the logistics behind the setting.

Cooler Reasons

• House elves are a kind of servitor - an artificially created magical being whose sole purpose is to act as servants, and bound to either a family or a house. They cannot turn away from their given purpose, but they shouldn't be abused and treated as property either.
• House elves are analogous to brownies. They have their own culture and society, and taking care of a house or family is a matter of status and pride. Wizards viewed their duties as subservience, and began to mistreat house elves. This caused a massive upheaval in house elf society. Many withdrew and stopped interacting with wizards. Those who stayed behind accidentally instilled a culture of accepting abuse in their descendants, who now remain trapped between bigoted wizards and disdainful house elves.
• Wizards, in their self-centeredness, sought to make the helpful house elves completely subservient to them, and placed an extremely powerful binding curse on the elves. Those who remain uncursed have banded together to break the curse and free their brethren.