Once again, you are only talking about the Starting XI. Please, count how many times during a season the same players who start a game play for the 90 min these days. I can tell you right now if you don't want to check: zero.
I agree that Kovacic does not offer anything up front, and yet he's still better passer than Caicedo who offers even less in the final third. That was the case before City signed him, wasn't it? So, I suggest that regarding Kova, the fault is in your analysis, not the player. My reading of his game is that he's an excellent short range passer, and master at keeping possession: he can withstand pressure by quick changes of direction and short dribbling having full control of the the football at all times.
You are talking about quality, or perceived quality as each to his own, but I'm referring to characteristics; what can a player do on the pitch versus what a different player can do even in the same position. Is one better than the other in every aspect of the game? I don't see that very often at this level exception to a few WC players. I usually see tradeoffs with most players.
Is Enzo better than RLC? yes, far higher value too. Can RLC do things Enzo can't do? absolutely! He has an aerial presence, size and power to play in tight spaces. Fact is we have very few options in midfield at this time, especially in terms of characteristics.
Lavia is a funny one though: I've been hearing he will help us in the final third, and now you are saying he will help as a DM; dunno where he will be able to help us, but so far he's just a fad.
And? He's still fairly young. Will you think the same if in a year or two from now he recovers his fitness and form, and delivers good performances for club and country? I tend to give credit to players who once played very well vs others who never did, but that's me.