The only problem with Keita is that he hasn't played a lot of games due to injuries. But when he did feature, his output has been fantastic.
Player recruitement remains the single-biggest area where even top clubs can massively improve. Some transfers at elite level are just baffling (who exactly scouted Kepa for Chelsea?). Liverpool have been excellent in that regard under current ownership and they have one of the best data analytics department around which allows them to stay one step ahead of the competition in the market. The Greek fullback they've just signed being a good example.
This is Keita's data from his last three seasons before joining Liverpool which made them buy him:
He wasn't injury-prone at all at Salzburg and Leipzig so there's every reason to believe he can go and reproduce these numbers over a whole Premier League season.