When my teams were in lower levels (around level 7-12), I regularly used free agent signing 3 star 30+ years old players. I could not expect these players are star of the team because their qualities were lower than the team average But most of them performed quite well and quite consistent. I loved to start one of two of them because they are more reliable than many higher quality players.

As my team level up, the team is better off financially and can afford to build a whole team of higher quality players. Then I cease to use those old players and I am not sure if they are still useful for 3 star or 4 star quality teams.