And I think it's unfair to say he "built an expensive mediocre team". The 2019 team was expensive because it included expensive guys who just won 108 games and a World Series. It included hefty arb raises and dead money that DD had nothing to do with.
They tried to run it back, as the saying goes, but the pitching fell apart due to injuries, tired arms from 2018 or whatever. The 2019 offense actually scored more runs than the 2018 team. and had a run differential of +73.
A lot of the remnants of the 2019 team were on the 2021 team that made it to ALCS Game 6.
I think you're a little biased against DD.
We all have biases of course.