Fabinho is a very good, multi functional player, who didn't have a very good last season and it cost him his World Cup place, though I'm sure he'll bounce back to his normal levels of quality. To say he's one of the most dominant midfielders in the league, when he hasn't played, is errant nonsense, especially when he wasn't even the most dominant in his position in Ligue 1.
Keita is a brilliant talent, who again wasn't quite as good last season after losing his head after last summer. But at least he can put in a strong claim to be one of the more dominant midfielders in the Bundesliga. But to say that he is in the Premier League, without him actually playing in the Premiership, and coming up the likes of Kante, KBD, Pogba, Silva, Fernandinho, is also nonsense. He could be, and he's in a better position to lay down said claim than Fabinho. But right now he isn't, by virtue of never having kicked a ball in anger in the league.