The delay is part of why I'm concerned, as well as his comment about, "So many submissions that its hard to sort through them all".
If the delay is because he and whatever other part-timers are working on real content to sell the update, then it could be a good sign. But this is Valve, and they've done shit all since 2018.
In reality, the delay is probably because ES cobbeling together some ungodly amalgamation of community slop with no staying power. If he pulls a Summer 2023 on MvM it could legit kill the gamemode. The MvM playerbase won't survive if they get divided.
MvM isn't like casual where you can just add more maps to the queue if you want shorter queue times. You need to queue for the specific missions you haven't completed yet.