They can't really say Apple and Samsung have to do this, everybody else doesn't. And they are by far the market leaders, so they sell the most phones ending up in landfills.

I bought it used, and with the expectation that I'm going to be on the hook for my own long-term maintenance and support, as is true with more or less everything I buy. (Full-time Linux user here.)

The sad reality is that the experience of running an off-brand phone with an easily-replaceable battery would, long-term, be much worse than running a locked-in flagship that LineageOS builds for.