@Dudapples
I don't think your results are caused by lack of player's experience or bad formation/tactics. I won cup and CL with avg. 20 years old squad. Instead i think main problem is form. Always check form of your players. It sometimes happens that when you have 1-2 players in bad form, whole team performs bad. Form is very important. If your best player (according to quallity) plays in bad form, keep him out of 1st team, bench him or use agaist weaker opponents, try to increase his morale and change position (if he can play on more fields than one). If his bad form continues, sell him.
Suggestion: although form is main reason, check your tactics too. I would suggest to avoid hard attacking or defending as basic setup and don't use too much red arrows.