This is a fun stroll down amnesia lane. Lots of well-regarded guys here. Let's start with the top 10 rankings (largely because that's where the rubber is likely to meet the road):
The 2017 minor league class included a nearly-ready Luis Castillo and Jesse Winker, Tyler Mahle (having just finished his first foray into AA), a recently-signed Taylor Trammell and Tony Santillan, and a whole host of young pitchers (Robert Stephenson, Cody Reed, Amir Garrett, Sal Romano), plus a dominating low A/ Pioneer League Nick Senzel. No one should have an issue with that rankings-- it compares quite nicely with others in baseball in that respect.
The 2018 rankings added Hunter Greene and Jeter Downs to a dominant AA Mahle (perhaps the best minor league season of the past 20 years for a SP in Cincinnati), plus the aforementioned Stephenson and Winker (who'd only played 40-ish games in the majors the season before and was largely still viewed as a prospect). This is the beginning of the Greene/ Tyler Stephenson era-- two prospects who are a long, long way away from the major leagues, toiling in the minors, and still well thought of. It looks like both will end up pretty solid players, fwiw, and both are still remarkably young.
The 2019 ranking added 2018 draftees Jonathan India and Josiah Gray to the mix and lost Winker and Mahle as prospects. India became the ROY.
What's interesting is that the emergence of prospects Castillo, Winker, Mahle, et al., largely was a driving force why the Reds went to the playoffs in 2020 and 2021. Too, they were able to deal from that storehouse of prospects for Trevor Bauer and Sonny Gray. It's apparent that better prospects (and better prospect farm rankings) probably mean better teams.