I really like the concept behind the game, and I've already spent a few hours in the game.
The game seems a bit overwhelming at first and the UI isn't really easy to grasp, but we get used to it and the gameplay is really neat afterwards.
Unfortunately, after a while the game feels pretty grindy, maybe it's just me that is doing something wrong, I tried to diversify a lot which apparently isn't the optimal play.
Killing almost all enemies, only for them to be replaced when there is only a few left feels really frustrating too, especially since there is no clear indications on when the enemies will be gone.
I've had a lot of fun with the game, unfortunately I feel like I've hit a wall where its too grindy and I'm not having fun anymore.
It's not just you: uinfortunately, the game does not encourage diversification enough. Worse still, some tech paths are just far from optimal.
I have stopped updating this game years ago, but I've worked on a sequel that greatly improves on the flaws you noted (i.e. there's a progress bar that gives a rough estimate of when the next enemy wave comes). Waiting for when I'll be able to afford an art designer.
Long is the journey until the concept reaches its full potential, and feedback is vital to adjust the heading, so thanks :)