Well, before is kinda too late if you get my meaning, but it might help other people, and it can help for a re-watch.
I am a late Trekkie, I didn't even watch all the movies if I'm not mistaken.
At Comic Con Paris, I remember Sir Patrick saying that you didn't need to watch previous movies/shows. I find that quite wrong.
I might be in the worst situation. As I watched some of the movies, I know some events in Picard are direct references to the movies (First Contact and Nemesis are quite prominent).
I assume I missed a lot of story references (I'm not talking about Easter Eggs, I consider them to be a different category).
So can someone list for me what I need to watch to fully enjoy Star Trek: Picard? I don't care about spoilers about Picard anymore, or by events of the movies/shows that are spoiled by Picard, but it might be good to keep the spoilers tags for others anyway.
By the way, I did find this Medium post about TNG on this site (I think) and it is in my to-watch list, so don't worry about the 'gaps' unrelated (I also have the one for DS9). I also consider by default the pilot and final of any show cited.