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.
I don’t know why you think Liverpool will not be able to compete in the upcoming Champions League competition. Is it that you underrate them that much or what? Because you don’t really understand, don’t forget what Liverpool did at the Premier League competition this season. They were trying their possible best to compete with all those big clubs, although they later went down and their performances started declining. But that doesn't mean they will not do more in the Champions League. Liverpool are also good enough to compete, so let’s watch and see how they will come through this season.