bell almost hit 40 homers in 2019. not sure why so many people are saying he's not good
he sucked in 2020 but that entire team did. wouldn't be surprised if he bounces back with the nats
He had a good season at the plate in 2019, but his two previous years were mediocre and 2020 was awful (but I'm skeptical of placing too much emphasis on 2020 results, given how weird it was).
Bell is a low average power hitter. He walks a decent amount and doesn't strike out that much, but he's about a .260 hitter, so he needs to hit 30 home runs and walk 70 times to be above average. He plays first base and poorly, so he's not useful unless he's hitting as well as he did in 2019, his peak year (and the only year he's even been close to an average player - the rest of his career, Bell has played like a platoon first baseman/pinch hitter, which would be fine on a roster in 1975 but which is no longer a role a team is willing to spend a roster spot on). Bell has to replicate his best season just to be an average player, and that season is now more than a year away and bookended by a lot of mediocrity, while Bell gets older and more expensive.
A below-average first baseman giving you 15-25 home runs on a league minimum salary is a fine complementary player, but at $6 million he's a luxury unless your team is getting a lot of cheap value elsewhere or is monstrously rich. Bell just doesn't have a lot of value unless he's hitting his peak every year, and I'm extremely skeptical he will reproduce 2019 again. Players with his profile (slow, zero defensive value, low batting averages, decent but not spectacular plate discipline, good but not outstanding power) don't tend to age well as they approach or pass 30, because losing just a little bit of bad speed or foot speed renders them totally useless at the major league level.