The problem isn't so much that Google has a hard time old phones on their OS maintenance team books, and even just phoning in the effort to keep them working (hah). It's that they actively don't want to do any work that isn't sexy and supporting new products. I don't think their teams are incentivized to do so.

Let me play it out with an example.

At Apple, a team/individual might be actively told to have to use an iPhone 8 for their daily use, so they get to experience what it's like for a user with an older phone. They solve the users' pain by solving their own pain, and commit to making the experience actually better with future iOS releases. Not just keeping it working but actually making it better if possible.

Google has shown time and time again that they're not thinking like that. Or at least not setting up the company to be rewarded like that.

I will also posit that the single-handed ownership of the iOS app store makes deficiencies fall squarely on Apple, so they are more directly blamed/responsible when phone performance gets worse. With Android, and so many reasons a team could claim that other factors are causing negative trends in performance, who cares to keep making an old phone better?