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 agree with you that Liverpool is not capable of performing in the champions league next season because among all England teams, Liverpool has the highest champions league record because they have won it 6 times while the second club from England which is Manchester united has won the champions league 3 times, Chelsea and Nottingham Forest won 2 times each, Manchester city has just one champions league title alongside Aston Villa that has also gotten one champions league trophy so this is to show that Liverpool still remains the highest team from England that has won the champions league.
Sure Liverpool will struggle to perform without Jurgen Klopp who have managed the team to a good standard within his coaching career with the club even though he didn't achieve many trophies but let us not forget that Liverpool have great talented players so they can perform better than they did last season even though they were not in the champions league last season but for the fact that they made it next season mean they will devote their time to make things work out well for them.