How deprived of all faculity of thinking must a movement become to come up with the idea of "solutionism" as a critique? There is a problem and people think about solutions. Any solution would, of course, be reason for existential difficulties of the problem. But the problem is the basis of power of said movements. When the problem goes away, so does the power that came with it, when the movement came into existence and so does the only solution the movement sanctioned: complete austerity and refraining from any use of technology and any interaction with nature as much as in any way possible.
"Solutionism" is the latest, most ludicrous and hopefully last, attempt at defending the only solution "environmentalism" ever came up - by denying the adequancy of any solution of their problem whatsoever. Thus perpetuating their claim to power indefinitely - you know, the UNSOLVED PROBLEMS of technology.
Go and rot in hell.