The movies I'd previously never seen have been a mixed bag...
Not the biggest fan of Iron Man, but Iron Man 3 was enjoyable once we established that the not-so-vaguely racist character of the Mandarin wasn't real. Even though I haven't seen Avengers: Endgame yet, I'm not immune to spoilers so I know how this character arc ends. And I don't care. Tony Stark is plain insufferable.
Captain America: Winter Soldier was meh, and it pains me to say that because I love Cap. The only useful thing it served for me was fully understanding what happened in the background of Agents of S.H.I.E.LD.
Avengers: Age of Ultron is the weakest of the Avengers movies, and also underscores why Tony Stark/Iron Man sucks. It also helped fill in some gaps from Agents of S.H.I.E.L.D. episodes.
Ant-Man was great (Paul Rudd usually is).
Loved Captain Marvel. It's the only movie I've had to watch out of order, but only because it came out later.
I'm now extra-motivated to make it through Cloak and Dagger S2 (maybe yay), Luke Cage S2 (yay), Iron Fist S2 (God, please make it stop), Daredevil S3 (End it now, o Lord), Runaways S2 (hmmm), The Punisher S2 (no no no no no), and Jessica Jones S3 (OK) so I can finally get to Avengers: Infinity War and Endgame and Agents of S.H.I.E.L.D. S6.
This project has lasted longer than I thought it would, but I'm glad I'm sticking to it, even if I have to take breaks to watch Derry Girls S2, Call the Midwife S7, and old SNL episodes I missed.