I agree with you that Champions League will be more competitive next season. The Leverkusen team is very strong despite not having many star players. On the other hand, Manchester City will try to strengthen their squad next season. Reigning champions Real Madrid have already managed to strengthen their squad by adding Mbappe to the squad.
Just by looking out the clubs we have already gotten an insight of how next season champions League will look like and the clubs that has a very higher chance of winning and also in the case of Liverpool I would say that they should just focus on the premier League for now because with what they did on this finished season I don't think they will survive on the champions League and also they are still going to go through a little declining in performance as there coach Klopp will no longer be with them next season, so getting use to the new coach will certainly take some time and also Arsenal on the other hand should also focus on the premier League more because that's were they have the higher chance on, however in terms of real Madrid they have already equipped themselves and they are ready for the champions League.
Every season of the Champions League is always tense and full of amazing things because of the matches of many strong and great teams, and for example like Dortmun who unexpectedly can be in the final party with great confidence against Real Madrid.
For Liverpool, don't be underestimated because the new coach is not as high as the popularity that Kloop has, some people think too much to underestimate Arne Slot without knowing what he might do with Liverpool in the current season, maybe they will dominate even more and close the mouths that think he doesn't deserve to be at Liverpool, it might happen because we know that next season will be good for all teams.