Reverse Flash had the psychological advantage of killing Barry’s mom, Zoom had speed and took Barry’s speed at one point, and Savitar was always one step ahead as he was a time remnant of Barry.
As to why The Flash went with The Thinker this season as opposed to yet another speedster, Todd Helbing might be hinting something as he tells Comicbook of the great care the team took into differentiating all the speedster villains.
Since their skillsets were all relatively the same (fast), the difference had to come down to the impact they had on Barry psychologically.
It’s possible they considered a speedster for Season 4 at one point, and then realized they were running low on ideas to keep it fresh and something more than a foot race between two metas.