First of all thanks a lot for playing my game! This is the longest feedback I've received since the start of the jam so I'll try my best to respond to everything in the best way I can.
The "interest" mechanic was something I came up with early on in development (like the first hour of the first day basically) so until I implemented it I kind of didn't put any more thought into it. When the time came to implement it and my friends playtested the game I noticed it had some issues and mainly what you described. The game is just too easy after the first few waves if you know how to use the mechanic properly. But I think I might be able to fix this by 1: lowering the cap to +5 for example or 2: just making the game harder. Although the latter would maybe make it too hard for people who are new and/or don't understand the mechanic too well.
Tower balancing (and mainly bombs) had been something I'd been tinkering with the last few days but because of lots of bugs being found and needing to be fixed and some feature requests from the people playtesting I decided to do those first and in the end just didn't have too much time to actually take an in-depth look at balancing. I remember during the playtests spear towers had a pierce of 10 unupgraded and 15 upgraded and cost like.. nothing (unupgraded pierce is now 4). The meta then was just.. place spears everywhere. So I'm glad I avoided that.
I get your complaints about not being able to do anything during the storm. I'm also the type to micromanage everything when I'm playing Bloons so it does feel kind of counterintuitive. I'm also a big fan of as little downtime as possible in games, but here I deliberately went for it this way because of the jam theme and I felt like if I let you do something during the storm I'd have abandoned my original idea.
Lastly the targeting. It's the most broken thing about the game and I've had quite a few comments pointing it out. (It also contributes to why the bomb is so shit). Spear and Bomb towers throw their projectiles towards a marker with a position on the enemy, but if the enemy goes too fast it just misses or is too far away it just misses. I know how I could fix this but it would take quite a bit of work (and math) to make this work properly because it would generally be a system overhaul. That's why I decided not to.
I'm really glad you enjoyed it and I was able to give you some more insight into why things are the way they are! I wanted to meet your comment's effort with effort back after all :)