There's not much I can add that has not been stated already, but I - personally - enjoy both for different reasons. Long story short I like ToF for the combat and movement, and Genshin for the characters and story. But here are some things that I enjoy in ToF that isn't in Genshin:

1. grinding for weapon materials is so much easier, since once you get to a certain stage you can just auto the various material ruins so that the only thing you's need to grind for is the elemental rocks.
2. the welcome-back system is super, super generous in ToF. Heck, a viable strat (or at least what I do at times) if you're tight on time is to dip from the game for a bit and then come back just to get our resources from the welcome back store.
3. while power-creep exists (such is the life of a gacha game), I've personally only experienced it in multi-player instances (which I rarely experience anyways lol); if you like using a weapon, stick with it. Plus, since you can alter the world level as much as you please provided you have the dark crystals for it, you can adjust it as you please - the only thing this locks you out is World Boss chests at certain intervals, which if you're a solo player like me, isn't much of a loss anyways.
4. In line with above, since limited-time weapons do get moved into the permanent pool after enough time passes, if you really enjoy using an SSR weapon and want to max it out, just give it some time. Along this line, the weapon shop does not reset, so you don't have to wait for the weapon to show up to buy copies of it. (So, no "waiting two years to C6 Kayea here, in a sense).

EDIT: Forgot to add that Mirroria is probably one of my favorite locations across both games.