Battlefield 1 is unique - like many other games - but in addition it is very playable and has a very good atmosphere. That last one is actually the most difficult one to achieve, and BF1 nailed it. Also, WW1, if you like that as an era, this game has no competition.
So, is it worth playing in 2021 ? Man, it may be the best FPS of all FPS.
I don't understand exactly why other Battlefield games (including BFV) seem to lack the same graphics of BF1, because they look awesome, and why they settled for less, in actually any subsequent Battlefield (which may end up including BF6), but that is something else. I guess it's the combination of DX version, ray tracing and game engine. I said it before; they nailed it in BF1, and NOTHING is on the same level, nothing.