The smartest thing you can do is plan out your game expecting that you can't do certain things.

For example, i can't draw people. I'd make a game containing only vehicles, non-anthropomorphic robots, etc and avoid the problem entirely. This also would have a lot of other benefits, e.g. not having to worry about facial animation, walk/run animations, etc.

Failing that, you can acknowledge that a modern game really isn't something done by one person, and find someone who can do the things you can't. I can't make music either, but i just go and find some on opengameart :)

Good luck!

You have hit on some little "cheats" that can work. The main thing with cheats like this is find a style that you can do, and stick with it. If creating objects out of geometric shapes works, maybe it can be a solid style for you and a game. You can then vary that up possible for a different style, say by using those filters, gradients, etc... In fact, maybe you could learn to create graphics with a vector program(Illustrator, or the free Inkscape).

The way I used to "cheat" for 2d graphics was by creating them as 3d models and pre-rendering them. For whatever reason, 3d was much more intuitive form me, maybe because I'm just creating geometry instead of worrying about lighting/shading. And though this method takes more learning time, and more time for the initial model creation, once you pass that stage, things suddenly get much easier. Need animation? Just do it with that model. Need to change something, do it and re-render any animations you have, no need to redraw a bunch of stuff. Need a bigger/smaller size version, just re-render. The same thing applies if you want to change the lighting direction. There are considerations to take with this. For example, the size can't really be 16x16, with 32x32 being pretty much the bare minimum for most things, and really not that great, more like 64x64 being a pretty good starting size. You also have to consider how you shouldn't model details that wouldn't show up in the final render, but remember to include some things that might show up if you increase size so you already have it in case. It's a balancing act.