I personally don't find it highly engaging yet. Don't be discouraged in any way by that, though. The potential is definitely there. I think finding the "metrics" that create fun for this game and then figuring out how to bump up those numbers through playtesting and iteration will take you far. Here's some metrics I feel could improve the experience.
- Time to Kill: I want things to die faster because it'll speed up the dopamine hits and thus keeps me hooked.
- Survival Difficulty: I feel like it's super hard to lose right now, which means that there's not a lot of tension. A lot of this is due to how much health I have. Lowering health would probably require lowering tracking on the enemy shots as well as it's fairly hard to dodge.
- Aim/dodge difficulty: Right now the game uses an auto-targeting system which removes skill expression in the form of my ability to aim. I think you can keep this if you're attached to it, you'll just want to make sure I've got room to express skill in other ways (like my ability to dodge attacks).
- Mechanic clarity: we already chatted about this one. Making sure I know how all the mechanics work ensures I have the highest chance of enjoying all your game's features.
- Mechanic and kill "feel": the better a feature feels to use, generally the more players will enjoy using it. More feedback on a kill generally makes killing something more rewarding, which makes players more likely to keep playing.
- Power up utility: run surveys with players to measure how useful they feel each power up is. Once you start getting 8+'s, you know the power up is solid.
There's definitely potential in the idea if you want to keep working on it. You've got this!