Because they're all not equal in ability and you can't just plug and play one for another without having some real consequences for team ability. So to just line up all the minutes and say it's all the same just isn't accurate.
For me you have Fabinho and Thiago as basically World Class or Great and then the rest all have issues of some sort that. Now we have Klopp and I trust that he'll always be able to jigsaw this together but it can be the difference between a title and not. The Spurs game for instance, it was a midfield of Morton, Milner and Keita. Yes we should have had a penalty and a red card but we also had absolutely no control in the game at all. So having to play two of Ox, Jones, Elliot, Milner and possibly even Keita in any combination in midfield could be extremely problematic depending on the opponent.
It also may not matter as any absences may just line up perfectly and we win the title on the trot, who knows? But if there's something you want to pick a hole in for why we may come up short then this is exactly it and why people keep saying we need someone else.
This is all fair enough but feel like massive cop out to the questions I asked.
So let's try and add a bit of granularity and break it down by midfield role. I suspect Klopp and his coaching staff do a more detailed version of this and scenario plan what minutes and combinations they may expect to have to play over the course of a season.
No. 6 position requires ~5000 minutes.
In my projection it's 3000 minutes from Fabinho and 2000 from Henderson
No.8 position ~10,000 minutes
Henderson, Keita and Thiago i'm predicting will take up over 50% of the minutes.
Elliott, Jones, Milner and AOC will take uo the majority of the remaining minutes. This will include a fair amount of minutes in the domestic cups, potential CL dead rubbers and last 15-30 min appearance in CL and PL when we want to rest legs.
There's obviously going to be times when injuries and unavailability mean we can't go with our main 3 midfielders. That wouldn't be great in certain games, namely City home and away, Chelsea home and away, Spurs home and away and probably United, West Ham and Arsenal away.
However, looking back at the games where we dropped points last season, it wasn't the games when we necessarily had 2 or more players from the 5th to 8th choices playing where we dropped points. In all but 2 of the games we always had 2 out Fabinho, Henderson and Thiago starting. The exceptions were Brighton at home where Keita and Henderson both started but I think Keita did go off injured. The other exception was Spurs away when we started Morton, Keita and Milner due to Covid-19. It was a ragged performance but those were exceptional circumstances that affected team selection that probably won't be replicated this season unless there is a massive injury crisis.
There's also a few examples where we started 2 out of Elliott, Jones, Keita, Milner and AOC in midfield. We won most of those games. The most notable of those being United away where we won 5-0. We also beat Atletico Madrid away 3-2 without Fabinho and Thiago playing.
I've said on here before that I would like a new midfielder. Probably to replace AOC. But I've also said it's difficult to do that swap and justify the the existing players how they will get minutes. Or conversely justify to a new signing, how they are going to get 2000 minutes if you still want to develop Jones and Elliott and give them game time.
Reality is that if we want a new midifieder then we'd need to sacrifice more than 1 of our current midfielders. That feels unlikely given how highly Klopp rates Jones and Elliott and how Klopp and the club pushed for Milner to extend.
That's my opinion but it would be good to hear a bit more detail on how you'd fit a new player in and where he'd get his minutes from and how that would affect others.