I genuinely think this is the case, and why products don't have a LTS interface, even though they ought to. Sign me right up for the 10 year LTS interface. I can't recall any features in gmail that were added that I actually use besides labels, which was an early launch feature. But it's been redesigned about 9 times in the last 20 years, each time with increasing white space and/or a slightly different font.
I can't think of a single feature my phone has gained since at least 2015 that I use. Actually it looks like the nav bar and material design 1.0 came out in 2011? The smart phone was largely "done" being developed by 2014. That's the year we got formal support for "use the flash LED as a flashlight" feature. Nexus 5 had wireless charging in 2013. Other than that the only reasons to upgrade is forced obsolescence or battery failure, or better quality phone camera(s).