This game is great, but there are a few issues, as mentioned by others. But to be honest it feels like the you might need to buff the shotgun, it doesn't do much damage and needs over a full clip to kill a big boi.
An idea I have, it's kind of weird, but I think it'd be cool if you could right click while holding a gun to be put into a certain "mode", like for example if you right clicked while holding a AR you would be faster with less health, or if you right click the shotgun its more damage and slower, and it keeps the buffs and debuffs no matter what gun you're using, and it has a cooldown of like 40 seconds after you use it. It's probably difficult to code but just an idea.