You can understand Klopp going for 3 workhorse central midfielders, rather than having atleast one creative attacking midfielder, with having fullbacks like Robertson and TAA. I can't remember the last time a team played with their wing backs being the 'playmakers' in the team and not someone centrally or atleast on the wing. Both of their defensive weaknesses are supplemented with the 3 midfielders covering space left by them and allowing them to move forward without worrying of what's behind them.
This tactic is perfect against teams that want to attack you because you can expose space on the wings, but then you can see why they struggle when teams are defensively sound because then you're exposed to just playing crosses into the box, which isn't easy to score from if you are dealing with a packed penalty box and no natural header of the ball. I think then you need more creative playmakers to play tight passes in the middle, rather than only crossing.