It really wouldn't.
I'm not sure why, but there seems to be a weird perception among some fans that our players are much younger than they are. Discounting all those but keeping the rest of the squad the same we'd have Pickford, Sidibe, Digne, Keane, Mina, Delph, Bernard, Gomes and Gbamin going into next season in that age bracket. That would be the huge majority of the squad. Even the likes of DCL, Kenny and Holgate will turn 24 in the course of next season, they're not kids anymore.
We have many problems within the squad, but the overall demography isn't one of them. Brands has done well to recruit to an average age of under 25 the last 2 summers (one summer we were the 4th youngest in the league for that, I haven't assessed 2019).
While it's true the majority or close to entering or have just entered the magic 25-30 bracket where you expect the best/most consistent performances from players as a squad most are just entering it. There is still some room for improvement, but as you say not massive strides. That suits the manager we have and the supporters expectations. I don't see any massive desire for a 3 year project where we are very inconsistent before it starts to get ironed out.
The expectation ought to now be, for Holgate, Calvert Lewin, Richarlinson, Iwobi, Gbamin, MIna, Digne, Pickford etc to start delivering quite consistently. Perhaps not markedly improved displays but certainly ones where there is greater consistency.
Either side of that group, you have the likes of Keane (though I suspect he will be sold) Bernard, Gomes, Sidibe who I still think can perform better. Not necessarily out of an age point, but because we have a top manager now who is tactically more astute (I use Bernard as the bets example of this). The other side we have Davies and Kean. We need to see improvements from them for sure. I think we'd all like to see more young players targeted and developed as well.
I do accept, you have Schneiderlin, Sigurdsson and Delph at the other end who will now be declining. However in general the squad demography is fine. I mean I listened to Souness go on about Liverpool having a young squad. Mane, Salah, Van Dijk, Alisson all turn 28 over coming months, Lovren, Matip, Henderson and Firmino turn 29+ soon. Wijnaldum, Robertson are all well into that 25-30 bracket too. So it could be worse for us from that perspective.