Thanks for chiming in. I would like you to check the many different open source implementations. Wikipedia has a nice article about it and from https://postmarketos.org you can see that the advancements in the phone market are coming more and more frequently.

This is also further underlined by rising prices/dropping availability of rootable phones on ebay and co.

The question shows that you‘re also not used to the dev community of the phone OSs. The pinephone was a very courageous project and a pioneer. It was never intended to be an end user device but a stepping stone. We are seeing massive improvements all over, with more than 250 devices being supported by postmarketOS and dozens of people helping.

Apples „use 5-8 years, then throw away“ policy only works for end users, not unilaterally. You can always sell your old oneplus6 to someone for reuse, not so much your iphone 6 although both are out of official support.