So on skyblock, ultra+ keys are somewhat rare, especially the higher valued keys (Divine and Galactic). However, it's very annoying when you use a key and get 5+ stacks of cobble. The voter and stellar crates have cobble too, and that's understandable since it's an easy way for newcomers to get cobble quickly. But for people who don't need it, it's a waste of a key and disappointing. I think that cobble should be removed from ultra+ crates, or at least given a lower chance of being picked.
I'd prefer just going with this thread here: https://www.mineverse.com/threads/change-the-crate-rewards.146862/ Some of the rewards in that thread might be slightly too much considering the amount of keys being tossed around right now, but the idea of it is nice - changing the rewards instead of removing them. Either way, support.