Thanks. I don't mind that you didn't address my question directly, because this is all relevant food for thought.
Every year I'm more disappointed by Google on pretty much every front. They really do seem to have jumped the shark.
If I do decide to upgrade...
Unfortunately I can't stand iOS. No kidding, I'd rather have a Nokia 5110. I've tried repeatedly, thinking "I'm just not used to it", but there's too much about the design philosophy that I find actively obnoxious. Strangely, I don't have this problem with macOS.
Maybe I can find another Android vendor with a better support policy, or if none of them are any good then just suck it up and buy the very newest of whatever to at least push the planned death of my device back a couple more years.
I'm getting a bit sick of this treadmill. I don't buy the defence some people offer that it's too much work to support the older devices. Having a security-only backports release series for old devices would be _trivial_ compared to the enormous piles of money Google sets on fire for shits and giggles on a daily basis. It's planned obsolescence, plain and simple.