Find the right market size
If you’re aspiring to be an indie app developer, it might be worth focusing on medium-sized markets. A small niche market might not be worthwhile financially. A medium-sized niche, on the other hand, could be enough to support you while also making your business less interesting to larger app editors. You would then reduce the chances of having competitors with big funding.
Making a truly mainstream app that everybody uses could be immensely rewarding but it seems way harder. First, you’ll need to find a novel idea that would be universally useful. There aren’t many of those. Chances are, someone else will have had the same idea and maybe some funding to execute it. What you have then is a VC funded startup idea, not an indie app idea. If you still manage to build the app and make it popular, Apple and Google might also like it and sherlock you (See E – Enjoy it while you can).
I’m being a bit dramatic here and, obviously, I dream of making a massively popular app. My point is that the success and survival of TextingStory might be related to the fact it targeted the right sized market. Pay attention to this kind of thing.