The appeal is collecting, followed by designing. The rest falls in between dialog with villagers and aesthetics.
Think Sims, the people who actually play the game versus the people who just built houses and cheated money.. But in this case you can't cheat money. That's the general audience in a nutshell.
Its not for everybody. The people I know who play it tend to be a variety of artists(industry, not just degree and at Starbucks), cosplayers, extreme casuals, and Nintendo loyalists including Smash players and Pokemon VGC.
I'd be surprised if a 7 yrold would enjoy it, but that's because I expect them to have the NA gaming problem of requiring a lot of twitch and fidget. If he's about creative, and the occasional survival.. Or survival to build in MC, then I guess there is a higher chance he would enjoy it.
The 8 plus scores makes sense if you know the franchise.. The last iterations since New Leaf(3ds) have been cuckshows with micro trans camp and wtf is happy home designer. New Horizon adds a fuck ton of QoL, additional content, and expanded upon multi-player. Other than that, it's a big Nintendo favorite.
Surprised to see a thread on FoH for it. Granted wife and kids makes sense.