I recently switched to Android from iOS, and actually don't find this to be too big of a deal now that mobile OSs have matured somewhat. I was excited to finally be able to upgrade to Nougat a couple of months ago, but there were precisely zero user-facing differences, apart from a few inconsequential aesthetic tweaks. I can see that it is more of a problem for developers, who can't use new APIs without drastically limiting their audience.
It is absolutely true. Outside of a few model lines which get directly supported by Google, software updates for Android phones are rare. This is one of the biggest causes of Android fragmentation -- for most people who have an Android phone, the version that came preinstalled is the only version that phone will ever have installed.