Great submission, even if it wouldn't be your first game jam.
Game design:
I like the realisation of your concept. It does make you dive into the climate of that world and your story is also something that makes you wonder what will happen next.
There are some changes I would suggest though. I lacked a bit of feedback from the game. Screenshakes are great and I'm glad you added them, but I believe it would be a lot different experience if you made particles in this game: for being hurt, enemies being hurt, destruction and some other little details. Also there is this common problem with enemies being stuck (it literally did make me quit on wave 4), and there might be solution to it like a minimap with enemies or a counter with enemies left (it would be a nice detail).
Fun:
It's a pretty enjoyable game, but the biggest problem with gameplay is shop. It's pretty hard to build something and also it's fairly easy to build by mistake. You could make shortcuts like 1, 2, 3 etc for building. It would make it easier to manage stressful situations and would make the game more fluid. Someone suggestion with player having some attacks is also nice, but I would rather change it for something like pushing/pulling/stunning enemies, as we want sentries to kill.
Innovation:
As I said I enjoyed the concept and all the parts when we were talking with classes were a great idea. You got a nice material to work on.
Theme:
I wished there were some more interesting connections to theme than a game wanting to kill us, however veiling it with plot made a bit of job there. Maybe if I could get to the end I would appreciate it even more.
Graphics:
Great job ;) Really good mood and nice style. The only thing I lacked were particles.
Music:
Also very climatic, however quality of SFX was a bit low ;/ but it was the jam where we had to create everything alone so it's understandable.
Great game ;) Hope for contination.