Perhaps, for the sake of leveling up, you changed the initial characteristics of the ship, so the game seems less fun. Since you continue to develop, then all claims are just comparison with the competitive version (I would write these comments if I saw this version at the competition). I believe that in the future all this will be corrected. Good luck with development =)
All is good! :) A game can not be a fit for everyone, but still all feedback is important to listen too. Also, i have only had about a total of 1 ½ weeks devtime on Zentaisen due to the competition and other stuff in life.
When you add new features and try them out, something else can feel less good and so on! Leveling up right now only raises the Max HP, and with money you can buy Weapon powerups such as bullet power, ship speed, extra lifes, bullet spread etc. The first version just threw you all the upgrades directly and i thought that everything just felt "too easy" almost.
But still, it needs to be balanced to not make it feel boring or lengthy in a bad way.
Thanks :)