This tierlist incorporates all relevant Marvel related shows based on how important each movie or show will be for understanding the plot for Avengers: Doomsday.
Fundamental is the tierlist for movies or shows that are a must-watch to best understand our main cast and the story and order of events, none of those movies can or should be skipped before watching Doomsday. They explain each major characters origin, beginnings, the core of the Infinity saga, and the TVA.
Very Important are movies or shows that should absolutely be watched if time permits, they introduce important characters, plot devices (like infinity stones), and world building fundamentals (quantum realm, mystic arts, multiverse, etc.) to best understand Doomsday.
Important for Lore and Filler are movies or shows that are required to best understand background characters lore and stories for world building and understanding the nuance and connecting all of the movies and shows together. Best example is Spiderman: Brand New Day incorporating themes from DareDevil and Punisher together frequently.
Optional and/or Reccomend are movies or shows I reccomend watching for the stories, not necessarily their importance to the plot. Edward Nortons hulk is good to watch because it is still referenced in the new movies like when Banner says "Last time I was in New York, I kind of broke Harlem". The TV shows that have recently come out are good watches.
Not Required are movies or shows least likely to make a major appearance or impact on Doomsday overall and can easily be skipped or overlooked due to irrelevancy or just blatant mediocrity (Ms. Marvel, Ironheart, and She-Hulk) Jessica Jones and Iron Fist (might) make an appearance but you'll get most of their pertinent information and abilities from Defenders listed further up. She Hulk is not worth wasting your life on.