One thing I've realized is that when someone calls Buddhism life denying, they're actually showing their whole ass. Because they're revealing that they either do not understand Buddhism (more often then not that is the case), or that they are rejecting the Buddhist cosmology of Karma, Samsara, and Rebirth. (Or both, its pretty much both)
Yeah I can imagine Buddhism would appear life denying if you don't know anything about Bodhisattva's or that you don't believe in Rebirth. If we only get one life, of course it would appear life denying.
Basically people with this take are either Abrahamic or former Abrahamic. Mainly christian and ex-christian Atheist. I wish these types would actually talk to a Buddhist, but that would require effort, and these types are allergic to such a thing. Easier to wallow in ignorance and arrogance i suppose.