I’ve never been a great fan of abilities being categorised either as darkside or lightside, I prefer to think that both dark and light are moral interpretations of the same thing.
when Rey did, it felt like an attempt to make force healing less inherently dark, which I didn’t like.
These seem like two contradicting statements. You say you don’t like powers to be inherently light or dark, but you do want healing to be inherently dark?
I think healing as seen in TROS is not a dark side action due to it requiring self-sacrifice (giving your life force to someone else). Ben could have been seen as fearing the loss of Rey when he healed her, but he knowingly sacrificed himself to do so, proving that it was really about saving her and not about getting what he wanted. Thus, this version of healing requires an inherent selflessness, and it doesn’t disturb the natural order of the living force due to being a net-even trade rather than rejecting death entirely.
Contrast this to, hypothetically, if Vader had been given the opportunity to try to save Padme in RotS. He would not have been willing to give up his own life to save hers. Padme was a possession he feared to lose, but he nearly killed her in the first place because he feared losing his own power more. If he had somehow found a way to preserve her, it would be through a different darker means.