PSG has enough players that they could actually do something that they would not need Messi or Neymar honestly because they have good enough players. I mean Mbappe is by far the best player in that situation.. However they have Di Maria and Icardi as well which means that they have a great roster without Messi or Neymar as well.
Mbappe is young and still can grow more. Because he is young, he can recover fastly after matches. Messi is already old and he now playing with his experience and skills that are sharpened in many years of his career. Neymar is no longer young and with his unprofessional style, he won't be able to take care of his body so well.
Di Maria is a player from the same generation of Messi and Neymar. Icardi is not given a good position in PSG and even he is a good player, he needs time and real matches, not training and on the bench.
I doubt PSG will go further in the Champions League this season if the coach cant find the best formula for his team. PSG's last few match in Ligue 1 have been very difficult because the players have struggled to score goals. It's not about how many star players you have, but how effective they are at creating chance and scoring goals. Messi only scored 1 goal for PSG, that too in the Champions League, when he return to France I hope he score more with Neymar and also Mbappe.
There is enough time for Ramos to recover from his injury and enough time for Ramos and Messi to adapt to PSG tactics and players there. PSG can wait them for Champions League but you are right, Pochettino must find a good tactic and positions to use Ramos and Messi.
Messi can be the key for PSG in big matches in Champions League. One free kick, one magnificent shot from Messi can change all. However, PSG must improve their defense and Ramos can be helpful for them with his experience. He can help only he is at his best. So far, Ramos did not have any match for PSG.
IMHO I think the job is too big for him to handle,if he doesn't get the right system of play into he's player's, Chance's of taking the Champions League is no longer sure.
Sergio Ramos is a defender that has shown the world he's best,still capable of doing more but he's he been paired with the right person at the backline ?
Messi as well he has Neymar alongside, expected much more than I'm actually seeing.
PSG are doing them self harm without selling Mbappe last season, letting a player that will give you 100 million go is a no brainier, too dumped for my licking......if Mbappe want a move he shouldn't be held back but granted.