You have 1 yellow marble, 5 blue marbles, and 10 people. 5 people want a yellow marble, and five want a blue marble. Blue and yellow marbles are just as popular, but the competition for yellow marbles is much more intense.
Even if we assume the App store today had the exact same number of consumers, there's many more apps competing for those users. The marketplace is very competitive, and the percentage of available users is less per app (on average).
My guess is that the reality is that the App store has many more consumers (or consumer dollars which is what we care about), but the number of apps has increased much more rapidly than consumer spending (e.g. supply increased much faster than demand).
How many flashlight apps were available 6 years ago? How many are available now? How has the average price changed? Given roughly equivalent ratings, how much research does the user have to do to figure out if one is better for their needs than another? How likely are they to do this? Are the per year proceeds of the average flashlight app higher now or back then? Even if we limit it to apps with a high ratings, how does it look? Are there other app store segments where the outcome is better or worse?
That said, here's something to think about: I myself have paid real money for a flashlight application for my smartphone. Why? Because I wanted a flashlight app that didn't take three screens and button presses to get to light, and I also was a little leery of what the ad supported apps were really using the network for, so I wanted one that didn't require network access. This was a few years back and on Android, but I think the point is applicable, what you think you know about a market on a cursory review may not turn out the be correct upon deeper inspection. Some people made money on these apps, either through advertising or through the initial app price.
Flashlight apps may have been a poor choice on my part, but I think the original point stands. How does the market for tower defense games look? What about platform games? Do you think the average developer in these markets markets makes as much as they did 5-6 years ago? Do you think the advertising cost is the same?
As for your original point, I'll grant that you have a point, but I don't necessarily agree with it. I'm finding it hard to speculate about markets where I have no actual data, but my hunch is that the market for tower defense games is larger today than it was 5-6 years ago (i.e. I think the genre has grown more popular). I don't know whether that correlates with increased revenue for developers of tower defense games, or whether the number of games has outstripped the demand for them. Although I think it's fair to expect that there are a few developers making lots of money, and bunch of developers making a moderate amount of money (that may or may not offset the cost), and a bunch of developers making very little money. It turns out the App Store in general has a very steep revenue curve, with most of the money going to relatively few developers. But I think it's always had that curve, we just didn't used to have the data available to see it as well as we do today.
I think the more important question with regards to the App Store is not "how much money are developers making?", but "how easy is it for a new entrant to make money?". And I don't know the answer to this either, but I would be interested to find out.