I see, it is a bit hard to create proper hit animations in 2D (this issue is being solved in 3D), but there are still some reactions to bullets (different ones for legs, chest and head) with a longer knock back animation if you hit enemies either quickly or with a powerful weapon (like magnum or shotgun). Previously in old versions it depended where you hit them, sometimes they ignored bullets but most of the time enemies fell to the ground and had to get up, on paper this sounds great, but it introduced some gameplay issues as the enemies didn't have much chance to fight back, so I decided to go with a more classic approach. I'm still planning to improve enemy reactions to attacks and adding more animations but I will be approaching this topic carefully so that the gameplay and difficulty won't suffer.
When it comes to ammount of enemies on screen I did some experiments like you suggested - less enemies, but harder and tougher but the testers said that the game got a bit boring and the enemies were bullet sponges so I decided to make them weaker but increase thier number. It is pretty hard to balance this type of enemy, but I got some ideas planned for future such as introducing new enemy type that would work in synergy with current ones.
Also I just want to say that I'm still here, I still care about the project and I'm willing to improve it, hopefully you might find the upcoming version a lot more enjoyable.
Anyways thanks for the support, I appreciate it very much.