I personally interpreted it as Luke being afraid that he would just make things worse if he were to get back involved.
I feel like I’m being a little flippant to say when you went into a much more deeper place in the rest of your comment, but that’s the text of the movie. There’s not really any other interpretation to be had, unless you want to get into really weird justifications, like, “Everything Luke says in TLJ is a lie, oh and also Kylo’s in on it too for no reason”. Luke is on the island because he thinks that leaving the island would hurt the galaxy.