The short period of time and lack of ability to really do much to enemies at the start made most of my time playing this feel like a slog. By the time I got through to the upgrades that actually feel meaningful, I'd gotten bored with seeing the same stuff over and over. Then the boss fight felt like just a test for if the player had gone through enough of the skill tree. In particular, the attack where she shoots in all directions didn't feel like something that could be avoided all, which gave me the impression tactics would be pointless.
That said, my biggest issue was at the very start. I didn't realize the tutorial continued upward, so I tried quitting out of the tutorial and starting a new game, only for the start game button to not do anything. I would've stopped right there if not for the comments on the game page mentioning the mandatory tutorial.