Stars are important, just stars do not mean that a player is a good player.
Sometimes stars can overcome some other bad qualities, so for sure it is always better have 5 or 6 or more stars... but I had some 6 stars players, whose performances were always and in any case bad.
Same, I had time to time 7 stars players that were really good, but 2 seasons after with 1 or 2 stars less, they were just normal, or even poor.
What I mean... stars are just a part of the quality of a player.