Manchester city and Chelsea are going to be strong this coming season though it wasn't that Chelsea was not strong per say but they were not consistent so that makes them look like they didn't perform well but at least they qualified for Champions league next season. I don't really know what to say about Manchester city but I believe they will do better this coming season and as for Manchester united, if they don't sign new players they will still suffer same thing next season unless Ruben Amorim will change the team entirely and that will take him a lot of time.
I agree with you that both teams will be stronger next season because Manchester City have brought in reinforcements in this summer window. Chelsea also have quite a number of good talents in the squad for the coming season now it’s left to Manchester United to make signings as we watch. They have brought in Cunha and are hopeful to complete other deals to strengthen their side for the coming season.