Some object on the grounds of PoW mining and its incentive structure; others due to their tendencies to disproportionately accumulate wealth to early adopters; yet others due to widespread predatory and/or misleading marketing. I‘m probably forgetting several other reasons here.

Personally, anything based on proof-of-scarce-resource is pretty much a no-go (unless it would suddenly provide benefits more than outweighing the damage it does), but definitely not only that.