“Plato’s Stepchildren” gets a pass, because Kirk kisses Uhura in it. Otherwise, yeah, it’s pretty poor.
Really, if you think about it, there are at least 10 episodes of Star Trek that are deserving of being considered the “worst”. I personally just lump them at the bottom and refuse to re-watch them. I mean, crappy TV is crappy TV; who cares if one or the other is that slightest bit crappier?