There's no better alternatives atm so there's no point calling for his head. Also a mid-season managerial change generally doesn't lead to better results except for some relegation teams.
However, I would think an end of season review would be due to determine if Klopp is the man to get us where we want to be.
Benitez may have lost the plot but right from the first season he recognised that our squad was weak and grinded results by making us hard to break down. If you look at top teams that have been punching above their weight in recent seasons(relative to the amount they spend) like Atletico and spurs their managers all started by building from the back. There has not been any title winning team, not a single one, that has a defence as bad as ours. The invincible Arsenal team in the early 2000s, all the iterations of man united's winning teams, barca, real madrid, ALL of them concede few goals even if they can score as well.
Granted FSG is also guilty of maybe not backing Klopp enough, but end of the day, organising a defence and coming up with a game plan is a coach's job. Simeone, pochettino has less resources than Klopp. Benitez inherited a worse team (traore ,smicer,biscan) and still got us to 2 CL finals in 3 years.