I feel like something of a broken record here but I'll repeat my position again for the sake of clarity.
I think how these things should be handled should be different to the extent an alleged breakdown is connected to the prospect of continuing to play for the team in question.
For example, it is entirely possible that someone becomes "burned out" on playing the game. That the prospect of training, travelling, playing, etc. at an NBA level is so distasteful to them that the prospect depresses them, and they are convinced that will not change. Considering the demands of playing, etc. at that level, my guess is that is not unheard of, and may be why many players retire even though they still are physically capable of performing. It may include things such as an unwillingness to be separated from family, etc.. I do not believe those people should still be entitled to any payment from their team. I also understand that the current CBA and perhaps some individual contracts may be to the contrary. That degree of discomfort, unhappiness, etc. may be so severe so as to meet the definition of a mental illness. I don't think that should matter because it is still tied to a willingness to play, and that in turn is the most baseline obligation under a contract.
So the question is -- does Rubio really, really still want to play in the NBA, but just can't because of an unrelated mental condition? Or is he just sick of playing, wants it to be over, but wants to still get paid? This situation seems to me much closer to the latter than to the former, but if he is in fact unable to play due to factors completely unrelated to a desire to play in the NBA, then I would view this differently.