Thank you for giving me great feedback!
For starters, movement definitely isn't very intuitive and that does lead it to being awkward (I'll add a tutorial in the future to try and reduce this feeling hopefully), changing rotation speed does seem like a good change too! For teleporting I could do space again, the only thing I'm not sure on is what to make the cancel teleport button, maybe just like press any button? It felt, at least to me, that it made more sense for it to be left click to teleport and right click to cancel it. I'll definitely give this more thought in the future!
For the bosses I can see how they get very similar in their attacks. To me I didn't really notice this probably because they were themed differently, but this is definitely something to look at in the future! I really like those ideas you suggested so far and I'll try to come up with some that may also make they feel different and/or gimmickier than others!
The black hole we tried to make one of the more interesting ones as well! We did default back to just "make it shoot projectiles" to have more time as the jam approached an end. For a future update I'll definitely look into making it a lot more interesting, those idea's you suggested seem really cool!
For bullets I like that idea of making it lose damage is it goes. Maybe I could give it something like a sweet spot range that it deals the most damage if you hit in that area? I can see how the current system makes it feel like you have to get really close to hurt the bosses.
Thank you again for this great feedback! It provides so much insight for what I can improve on in for the future of this game!