If Manchester City also makes changes to their main squad, namely by recruiting new players in the back line, of course this could also make it difficult for opponents to move, especially if they meet Madrid in the UCL next season. If you look at the strength of Manchester City, they are still not strong enough in their defense. So there is still a lot that needs to be changed and Guardiola should be able to see that it is also important for the back line to be given additional new strength from new players who might be better than their current back line players.
Manchester City don't have to do many things, they only need to change the goalkeeper, that's all. All of Manchester City's defenders are strong, their problem might be find replacements for veteran player like Walker, but the quality doesn't have any problem.
Brazil didn't even include Ederson Moraes for Copa America, Pep should be aware with this because if Moraes is a good player, then why he didn't get selected? Dorival Junior choose Alisson and two goalkeepers who play on Brazil league over him.
They are still very good, but they have to make some changes to make them even stronger. Every time a club has to make changes, even if they are relatively small changes. The problem is that when they are still at the same strength, it is feared that they will be read by their opponents and at the same time other clubs will also make changes to make them even better.
Pep Guardiola certainly understands this, because he is a very experienced player so he will know what he has to do to make his squad perform strongly in all the competitions they participate in, one of which is the Champions League. Their failure this season because they lost to Real Madrid will also be a very valuable lesson for them. How they dominate the game but they have to lose, that is something that is not good for them. Therefore, they will also try to improve their performance.
Just one or two players would be changed but if you ask me, I will say that there is no need to make changes but to make an additional. Manchester city lost to Real Madrid in a penalty shootout which is always known to be a lucky means of winning. So I would not say that they performed badly in that match. In penalties, Real Madrid are always favorites because they are all professional players.
Next season will be a good one for City, but if they cannot still win UCL, it means that they have not improved. This is because Pep should be preparing and stay focus on UCL since City is used winning EPL just like Real Madrid is doing.