İlkay Gündoğan's desire to leave is nothing but that he wants more minutes to play and at Man City the competition is very fierce and it is possible that İlkay Gündoğan will not get full minutes of play, that is very natural for a player.
İlkay Gündoğan's performance is still quite good so it's only natural that many top European teams want him.
but on the other hand I think that İlkay Gündoğan's departure will not have a big effect on the Manchester CIty team, Pep Guardiola's team already has a very strong character, even if several players leave, it will not have a big effect on the team's performance.
Even if Gundogan leaves Man City at least Pep Guardiola will look for other options, it's just that Gundogan contribution to Man City is quite significant and without Gundogan I don't think Man City will have made it this far in improving their performance. To be honest, Gundogan, who was appointed as Captain, explained that his role was vital enough that the decision to extend the contract was the best option. Apart from that, Arsenal and Barcelona, who had been eyeing Gundogan for a long time, had to look for other players.