There's a lot more to consider once you look at how the entire app market is changing, rather than just the very top.
While I'm more tech savvy than most people I know, a lot of my friends have uninstalled the Facebook app as well, for a variety of similar reasons. Several have noticed what a battery hog it is, others got pissed off when Facebook added the messenger app, and others did it for privacy reasons.
Interestingly, I've noticed I use Facebook a lot less since deleting the app. I should see how my friends usage trends compare. I wonder if the friends who deleted the app have noticed a decrease in their Facebook usage, or if all my friends have decreased their usage and it's just a function of us being older/in different stages of life.
My bank is barely competent to use HTTPS with valid certificates - why on Earth would I chance using their new-and-untested app when I can't see if it's worse than their website?
The other answer is loans. If you get a good rate on a mortgage through a tech-illiterate bank, you're pretty solidly locked in.
http://www.cnet.com/news/firm-finds-security-holes-in-mobile...
Meaning that there are only so many people on this planet, only so many of us have a smartphone, and only so many of them again will be interested in installing a certain app.
Meaning that sooner or later that growth curve will flatten out.
And apps are just one example, the pattern repeats across all markets.
At some point you should be praising the fact that the other end of the bell curve has not kicked in, not worrying about growing further...
I do think it's somewhat likely though that top apps show similar trends as the rest of the apps. Saturation plays a role, but it's probably limited. Many of the top apps like say Facebook were likely to be on a very high percentage of smartphones 5 years ago, as they are today. Yet they used to grow faster than they do today, which indicates that there was significant growth in the number of actual smartphone users driving the growth of app installations. In short, not just market share but market size, too, and that latter factor affects apps regardless of popularity.
That raw smartphone user growth has dropped off significantly.
Let's not forget that smartphone sales have been linear for a while, not exponential, and in some cases (see Apple's latest results) even shrinking. And that's sales, which includes replacement units. If you actually look at new active smartphone users, by very definition that growth factor lies below sales growth. In rich economies (those where the ARPU is an order of magnitude greater than low-income regions where you're still seeing substantial new smartphone user growth, driving much of the app economy), the growth of new users is way down. Between 2010 and 2015 the US saw smartphone users triple, it's forecasted to only grow by a quarter from then on to 2019. And that plays a role for any app regardless of popularity.
What I do think is crucially missing from this article is that if you talk about the app economy, you can't just talk about user growth. The app economy is users * ARPU. That latter part is completely ignored, despite signals (particularly among the top apps they're analysing) that ARPU has grown quite substantially.
For example, Facebook grew its worldwide ARPU by roughly 30% in the year ending on Q4 2015, about 6 months ago. In the US it grew 50%. So even the raw smartphone growth figure I referenced to grow by about 25% in the US between 2015 and 2019, is blown out the water by a single year of FB revenue per user growth.
Here however I think there is a big difference between top and 'other' apps. Without any data, I'd guess that ARPU may actually be down for non-top apps, due to a flood of competitor's driving prices to zero, whereas top apps tend to get better at monetising their user base. I wouldn't be surprised if the app economy is more lopsided in terms of revenues than it was a few years ago.
App boom is definitely over, but not nearly as 'over' as user growth slowdown would suggest.