It's TF2:MvM, and it's as good as MvM or even *better (if TF2 only had *[engineer and soldier]), and I wouldn't say it was stolen from TF2.
It's like the Valortant vs. CS situation, and even despite that, MvM is just tower defense, but you are the "Pawn."
It's hard, but not so hard that it's impossible to win.
You just need to find the right buffs for your playstyle and character class (the wizard in solo is the hardest for now, imo).
The only bad things, IMO, are
-New players (or non-TF2:MvM players) could be confused about map layout or objective (took me a round to realize that the map layout is familiar).
- I hope that the map is still WIP and this is mainly a blockout. The spawn area and the area right before the bridge.
-Small number of character classes (2 (AOWT) vs TF2's 9, but 4/5 would be enough)