I haven’t always used these particular apps to solve these problems, but it takes a lot to change my mind on one. If you make another RSS reader or Twitter client, there are certainly a lot of people who could use it, but you’ll need to compete with very mature, established apps. Competing in these categories isn’t about price: it’s about relevance and attention. If you can’t find enough customers here, it’s probably not because you’re charging $2.99 instead of $1.99 or $0 — it’s because your app isn’t convincing enough people that it’s worth using over the alternatives.
This is also the same problem I run into every time I'm sent new apps to review: is this going to be better than Tweetbot, Fantastical, or Drafts for my workflow? Should my readers know about this app even if I won't use it every day? How do I balance the expectations of my readers, who want to know about new apps, with my personal opinions and workflow preferences?
I've thought deeply about this, and I concluded that, ultimately, my readers prefer honesty over quantity of mediocre app discoveries. When a new app comes around and it improves substantially on my workflow, they deserve to know about it. From my perspective, I have chosen to remain curious while having high standards for the apps I'm interested in.
From a developer's standpoint, I agree with Marco's article. The 2013 app market is fine if you have the right idea, executed well at the right time. In four years of writing this site -- it was launched 9 months after the App Store -- I've learnt this: people like new apps, but they expect a certain degree of quality and functionality from modern iOS apps.
Again, like Marco says, the bar is higher today. But it doesn't mean developers can't still raise it.
Today, the App Store has other problems.