You're severely overreacting lol. First of all, by wRC+ Bo did better in 2021 than in 2020.
The "gone down every single year of his 4 year career" can be explained by:
Rookie year: only 212 PAs
Sophomore year: only 128 PAs, shortened season, pandemic, couldn't even play in his home park
Third year: his only actual full year, split between three different home parks
Fourth year: is 2/3 of the way through, he can regress to his mean
Bichette is whiffing and striking out more this year compared to last, while walking a bit more. His BABIP is the lowest in his career, so maybe that's regression to the mean or he's just being unlucky relative to his true talent. His avg. exit velo is 85th percentile, same as 2021, hard hit rate actually better - 89th percentile this year vs 83rd in 2021, barrel rate about the same, and there's nothing glaring in his batted ball data that indicates his swing has changed.
Bo is fine, he's basically a ~120 wRC+ true talent hitter which is reflected in his projections, and due to his swing happy tendencies is prone to being streaky. He's likely not a 140 wRC+ monster like his rookie season, but still a very good hitter that should slot within the top 5 of the lineup.