We started small and with no obvious path for going from the app we'd made, to running a company. Nevertheless, we were able to figure it out back in 2002, and it's gotten easier since.
It's slightly more work to sell outside the App Store, yes, but it's really just not that difficult. If a developer plans to make a living, or even just side income, from app sales, it's work that's worth doing.
If you started in 2002, and particularly if you have been actively link-building since then, you have a huge advantage in terms of visibility SEO-wise.
It's quite simply much harder to build a link profile in 2017 than it was 15 years ago.
It's not impossible, but don't underestimate the difficulty of starting up now. I started things in 2002, I'm still starting things now, and building an independent web presence now - at least, one which anyone will find - is considerably more difficult.
(Technically it's much easier - getting the actual website serving to the Internet is easier. But that was never the hard part.)
It's slightly more work to sell outside the App Store, yes, but it's really just not that difficult. If a developer plans to make a living, or even just side income, from app sales, it's work that's worth doing.