Legends certainly has potential, but the trailer looked really rough. As you said, it's still a year out, but I don't know if Game Freak is capable of fixing this in a year. I think the early 2022 date isn't something they actually expect to hit, and they gave themselves plenty of actual time in case they need to delay until holiday 2022.
Sinnoh is my favorite region and I've always wanted a Pokemon game set in the past so this game could be perfect for me. My fear is that it will end up like most open world games and it will just be an empty map with nothing to do. If the village from the trailer is the only village in the game and everything else is wilderness then this will be such wasted potential.