Watching The Search for Spock on SyFy right now, even though I own it on Blu-ray. It really is an underrated movie.
I don't recall any hate for it in its day. TMP had polarized fan opinions, and ST II seemed to appeal more to the ones who'd been disappointed by TMP but had not yet stomped away from fandom in anger.
ST III was great fun, even though Australia had to wait six months attempting to avoid spoilers. Down Under, Sydney fans had a very busy couple of weeks attending two free gala previews in costume and then opening night.
Then came the popular success of ST IV and it was probably about then (and definitely confirmed by ST V) that someone suggested the "even-numbered Trek films are best" truism. And even people who barely remembered ST III began to diss it.