There are many lists with recommended/must-watch episodes. But they usually just include episodes that are considered good or great.
Is there also a list with episodes that are important but not necessarily good? By important I mean episodes that introduce new concepts or new characters (or kill off important characters), or that have lasting repercussions in the overall story of the series or Star Trek as a whole, or are necessary to watch first for a pay-off way later.
For example, TNG’s “Skin of Evil” shows the death of a main character but it’s hardly a good episode. The same goes for DS9’s “Life Support”. I wouldn’t exactly call ENT’s “Storm Front” good either but it’s important to cap off the temporal cold war. TNG’s “Ménage à Troi” shows Wesley being promoted to Ensign but the rest of the episode is rather mid (except for the Picard meme) so that it wouldn’t ever appear on any must-watch list. etc.
“Datalore” is another one that’s important, but it’s not very good. Most of the episode is Wesley running around trying to convince the grown-ups that Data is being weird and being ignored. It’s the one where Picard tells him to “shut up”.
Yeah, I recently rewatched that episode and was really annoyed by it. The story only works because every crewmember behaves like a completely naive idiot.