Yes, I know it's "just" a demo at this point, and as such it's missing a lot of functionality. So, I'll update my score as more content is added, since there's a lot of room for growth. A low score isn't a reflection on you a game designer, its just the amount of room for improvement of this game specifically to other games on the site. So don't be discouraged by a low score, rather, just work on making it or the next game better :).

General Comments:
1) MOVEMENT AND MAP LENGTH - I think the player movement speed is too fast. Right now It takes me less than a second to beat a level due to movement speed and the map basically being a single frame. So, think about like this, if I only experience your level for a few seconds.. I'm not really getting much of an experience from it. I would focus more on making your levels much longer first rather than having so many.
2) MAP SIZE - The size of the player/enemies in relation to the rest of the world map is too large, basically everything is scaled so big and your levels being single screen make everything go by too fast. Again, the size makes it hard to experience anything.
3) CONTENT / GOALS - You call this game "Scrap Chase" So I was expecting to have to chase a runaway something name scrap, or collect scrap, something loosely related to the title. You have an announcer at the start of level 1 (that doesn't stay on the screen fast enough, btw), indicating that I'm working for someone else doing something for them. But we don't really get a feel for what that is. Think about who our character is, what we're doing, and sort of lead us through that. A game can be a quick exercise to test out mechanics, but that's not really fun. A fun game has a goal.
4) TOO MANY KEYS - I think it's a good practice to reduce the number of keys as much as possible. It just adds a layer of complexity to your game that makes it less fun. People are used to WASD / Arrow keys / SPACE. If you want to use Arrows + ZX<SPACE> that's a good setup, but then you don't really need the mouse.
5) RELOAD - This should probably just be automatic on a short timer, and so a key you can easily remove. Unless you have special weapons with limited ammo, having to reload is just distracting. That type of key movement is more appropriate for large groups of enemies and something that is more of a shooter-type game. Your game is heavily and mostly side-scrolling platformer.
6) BUG - NO TURNING BACK - I can't shoot to the left/behind me, even though I can walk that way.
7) BUG - PACIFIST - Once I try to turn around and shoot and die, causing me to reset at the start of the level, my bullets no longer shoot from my gun, but instead my bullets just spawn AT the gun and stay there no moving forward.
8) Badges don't work with Scratch games. You can take them off.

It's obvious that you put some thought into character designs and level themes. I'd say you really need to make your levels a lot longer, and help us understand a little more story.