Even though basically Pep Guardiola can rotate his players to be in De Bruyne's position, I think he really hopes there is a suitable De Bruyne replacement this season. De Bruyne is likely to be out for a very long time this season with several rumors suggesting he will return in 2024, obviously this is not good news for him so Pep Guardiola needs a replacement rather than using another player in the squad.
I don't feel Pep Guardiola need to sign a new player for the role of Kevin DeBruyne to be filled, Manchester city have alot of midfielder that can take over the role until he recovers. They have Bernardo Silva that just signed a new contract recently that can take over from where Kevin DeBruyne left and he'll do a perfect job because he has similar characteristics as Kevin DeBruyne as they're good passer of the ball but nobody can replace Kevin DeBruyne because of his quality on the ball. The Manchester city midfield also have Mateo Kovacic would is also a good midfielder and can hold possession of the ball and control the midfield with Phil foden also been in the picture so the Manchester city midfield has a lot of players to fill in the shoe of Kevin DeBruyne and now Pep Guardiola just have to trust one of them to do the job appropriately.
I believe that the times have changed a lot for Barcelona because for some time they have been a really unique club and were the first address in European soccer for most of the world's best talents. Many of their top players came from their own youth and have all been among the very best. But this is different now and since all those players from this huge era are gone (like Iniesta and Messi), the success also stopped kind of. They are now not this club that everybody wants to go to and they have a harder time to convince the top players to come to them instead of Real Madrid or Manchester City.
Manchester city and Real Madrid had something that Barcelona didn't have and that's the financial backing to sign all this top players that are making waves recently and not because Barcelona is no longer a top club. They still have a history and player would want to sign for them instead of other clubs and this came to display last season when they had transfer window war with Chelsea on some top players that both club wanted and they choose Barcelona over Chelsea on all occasions and that's to show that Barcelona still got what it takes but they're lacking the finance backing to actually chase after this players as they can't offer them the same wages as those these other two clubs will offer them and players are going where the money is this days.