Ah, sorry, mea culpa I thought the 7 and 8 were getting the same updates.

So the 7 is stuck on 15, and it is the one being left out courtesy of 15. Still doesn't address the submission though that is claiming this about the 8 and 16, which as of now is still very widely supported. I assume the author is just reading the tea leaves and predicting what is ahead. Eventually 16 will be deprecated too, though it isn't right now.

FlightAware on the App Store likely works perfectly, though it would require 16.4+ on devices like the 8 or newer. The "you can't use this anymore" is likely a startup API check on previously installed and no longer updatable versions.