I know it's beta so it's going to be extra slow to get in multiplayer matches but the concept of needing 4 ppl to play a match is outdated. You should be able to do 2 ppl missions, or atleast have AI as placeholders for people who want to play privately with a friend or two.
Also this may be a more difficult concept, but the ability to join multiplayer matches that already started would be appreciated, especially when players lag out in the future. Apologies if this was already addressed and more multiplayer modes are being presented than shown in the beta.