The coach is just an important part of a team in setting game strategy, setting game plans, and giving practice portions to the players. The quality of the players and the quality of the coach technically will help a team to win titles, but when a team doesn't have good squad depth, then of course they have difficulty winning titles.
In fact, winning the Champions League title will not be easy even if a team works with a great and experienced coach. Luis Enrique won the Champions League with Barcelona, but cannot guarantee the same achievement for PSG. Likewise with Pep Guardiola when he coached Bayern Munich and the same thing for Ancelotti when he coached Chelsea, PSG and Bayern Munich.
The coach is quite influential in the depth of the team because a genius coach will be able to make significant changes for the progress of the team. There are interesting examples such as Spalletti who was successful with Napoli, although if you look at the depth of the team, of course Napoli is not reinforced by big names or star players, but Spalletti was able to bring big changes to the team.
So, there are several great coaches who will fight next season to bring their team to the UCL trophy. Like Ancelotti with Real Madrid and Pep Guardiola with Manchester City and Tuchel with Bayern Munich. I think these 3 coaches have more impressive experience in the Champions League. I believe their squad depth is also very strong.