No matter how many new players being added to the Fenerbahce's squad, they will never improve. They are still having unsolved problem, which is related to their coach's strategy. I also aware about how horrible their coach subs.
I may be wrong, but they have to replace their coach if they wanna play better. I don't underestimate their current coach. Their coach lacked of creativity to try different srategy that can fit his club well. If they can sign a coach who can explor a better strategy, they can play better.
It would be a big prejudice to say that they will never improve mate. I agree that it is related to strategy. Mourinho tried to use the same system he used in the Anderlecht matchup. But it didn't work against Rangers at all. Now he needs to change it in the rematch.

Mourinho is actually a winner manager in European tournaments. He achieved Champions League trophies, won each one of the Europa League and Conference League once as well.

If he is given time maybe he could achieve such trophy with Fenerbahçe too. But for this year, his job looks really difficult.