Also Spock's Brain is really not that bad of an episode, just a bit more campy and hamfisted than the usual TOS episode. Voyager's infamous episode Threshold is far, far worse of an episode, and honestly a lot of TNG Season 1 is probably worse too. Something I think people used to 90s Trek miss about TOS is that it's not simply a show about adventure, it's a lot more about open-ended philosophical questions. It's kind of a culture shock coming from newer Trek, but it's still good if you go in with an open mind. But it's still a lot campier regardless.