We are underestimating him too much, Green is a star player for a reason, of course, he will still be effective in other teams because of the coaching staff will make sure that once they acquire him they have a system that will fit for him, imagine giving him a max salary and not using him effectively, that's insane.
That's not underestimating but a valid analysis.
Green is more effective clearly when he's with the Splash Brothers. He already used giving these 2 a clear shot. I'm also with others that he might struggle on other teams, especially since his trade will happen at this point of his career where we can assume he's not already in his prime.
Understanding the team's system is easy but it's not that simple to execute for some players especially Green that whose entire career is playing for the Warriors.