Experience inevitably seems to make people jaded eventually to where they no longer get the same thrill out of whatever they were interested in. I'm someone who gets burned out very easily with anything I'm interested in, and that's why I've picked up such a variety of interests in my lifetime. Even when it comes to music I've switched between genres liberally: classical, jazz, pop, rock, metal, prog, folk, etc. Even if I narrow it to classical I've tried to explore all the major composers and era to a significant extent so I've never gotten stuck in one sound/style.
My recommendation for people anytime they speak of getting jaded/cynical with anything is to switch it up. So you say you're not thrilled with Sibelius because you listen to him and hear too much Mahler; well, why not listen to something completely different, like music from much earlier or much later? Come back to Sibelius when Mahler is less fresh/present in your mind. So much of our tastes are going to be governed by not just our general experience with music/art, but also by the temporality of our experience; meaning that listening to someone like Sibelius just after Mahler is likely going to produce a different effect than listening to him after, say, Josquin or Carter.
There is definitely some truth to the "ignorance is bliss" aphorism, as when you're new to something everything is new, fresh, even magical in its own way. People often wish they could go back and experience X art for the first time, as there's simply nothing as powerful as one's first experience, and that sentiment holds not just with individual works but even to entire mediums/genres. I think it's a rare person who can spend their entire lives immersed in one thing and not go through periods where that thing loses some of its magic; but the only way I've ever found to deal with that is simply take regular breaks from it and come back later.
