I feel like too many people don't realise yet how big of a deal this actually is.Also being able to place objects outside of your house will lead to way more personalization in people town.
Villages will look nothing alike what we're used to.
You can create back yard not only to your house, but even to villagers' house (as seen in the first pic lol)
I can't wait to see how people will customize their towns.
Also, like you said, customisation of the character is huge. It has been introduced already in the spin offs, but it's finally here in a main game, especially skin tone.
And the clothes are way more stylish than before. Way more diverse, more realistic, cooler.
New Horizons will basically be by far the most customizable Animal Crossing experience.
Also, the Nook Miles system seem like a fun objective-based system. There's stuff like "collect X fish in a row without missing one", or "get X recipes of crafting", I love this kind of fun, stressless, little objectives.
The craft system, I see a lot of people being affraid of it, talking about how crafting is stressful, complicated in games... This right here seem like the most stressless crafting mechanics you could imagine lol. Just collect some stuff at your own pace, get some new recipes of crafting (we still don't know how, probably the Nook Miles can be a way to get some), and craft the stuff you like.