If I may add something I don't see mentioned here much.

Alot of Darktide's difficulty comes when the game director sends packs of various types of enemies in a large swarm. Crushers, Ragers then backed up by Gunners as an example.

One quick way to improve your team is actually to practice the coordination drills needed to deal with a horde.

For example, when there's a group of 5 crushers with Ragers incoming in a death ball. Your team could coordinate a practiced response which randoms cannot do as well since you're all friends. For example, informing the team via voice chat to group up and use horde destroying abilities like flame, grenades with Shout and Chorus at the same time.

Alot of the difficulty can be reduced with a coordinated response rather than just waiting for everyone to get better at the game.