#1: Kansas City Royals
Since 2017, the Royals have been building their team back up to become World Series champions again, like they were in 2014. They have done an amazing job so far with the prospects they have been able to either acquire or, most of time, draft. Developing what look like future stars on a playoff contender for years to come
If you want my full breakdown on why the Royals are the best rebuilding team in baseball, you can follow the link here.
In summary, the combination of current MLB players being average or well above, with a quartet of young hitters coming in who look like they will contribute to winning as soon as they get the call. A team committed to strong defense, speed, and overall hitting ability throughout their lineup.
The pitching has not fully presented itself in the majors, much like the Detroit Tigers, but there are several pitchers in the Royals rotation currently that look to have top end talent with a couple still coming up through the system.
Kansas City could have one of the most well-rounded but also just overall talented rosters in baseball in a year or two. That is why I think, at this moment, they are the best rebuilding team in baseball.