The movies did a great job at presenting thanos as an extremist that sincerely wants the greater good by questionable means, but it falls apart because his grand plan is just so stupid. The only way to reconcile the sympathetic character with the dumb plan is to point out he’s “THANOS THE MAD TITAN”, not “THANOS THE TITAN THAT FULLY CONSIDERS THE CONSEQUENCES OF HIS ACTIONS”
Would have been much better if they just kept his original motivation from the comics: Death is a hot lady and horny thanos does the snap as a gift to her