There are a dozen apps that do the same thing as yours ((If there aren’t, you’re either crazy, or there will be soon.)). To stand out, your users must to be delighted by your product - from icon to settings screen. You get there by designing, aligning, and refining each screen, nook, and edge case.
Most programmers act as if their ability to program prevents them from making something look good. This is bullshit. There are hundreds of counterexamples, ranging from Loren Brichter to Mike Rundle. You get good at design exactly the same way you get good at programming: you do it badly enough times to become mediocre, then you do it mediocrally until you become good.
Maybe you don’t enjoy design, which is fine. However, most engineers haven’t really tried it because they think they’re incapable. If you’re really unsure where to start, do a bit of reading about spacing and alignment. Spend some time trying to reproduce a nice-looking button or effect. Pull apart somebody’s .psd and reverse-engineer it.
Then here’s what you do: next time you’re tasked with adding a feature, take a serious shot at how it should look. Do your best to line up that new button with the existing ones. If the existing styles in the app clearly won’t work, try tweaking one until it’s close.
Your goal is to add a new feature, then have the designer that usually fixes your “programmer art” leave it alone ((Admittedly this was very hard at Apple, but I got pretty good at it. The trick was to find some function or edge case that had yet to be mocked up by Design, and implement it so well that it looked like it had been reviewed.)). It may start small - an error message or edge case, or a new element that just needs to be well aligned and balanced with what’s already there.
The more design practice you get, the more opportunities it will open. The prototypes you present to superiors will become more impressive. Your personal website will stop looking like it’s from 1998. The designer time spent on your features will go to polish and “wow” instead of just getting things up to par with the rest of the product.
Before you know it ((Well actually, after thousands of hours of practice, but close enough.)), you will have become a unicorn. That’s right, every startup’s dream: a Desingineer. You’ll likely continue to focus on programming, but you’ll have become more powerful than you could possibly imagine.
Or at least, you’ll make wonderful looking products that people want to use. That’s a good start.