Their A series is just a lag time for feature creep (or in this case, removal). For example, we got headphone jacks and expandable storage in A-series for now, but give it a few years they'll be where the S22+ are today. It just takes longer. Plus they're still too darned big. I don't want as 6.5" screen that barely fits my hands (or gesture controls that are horrid for those who've had early onset arthritis since their 20's like me...for the love of deer, please stop getting rid of buttons)
Believe me, if something worth upgrading to existed I'd be all for it. I'm not that closed minded. I just ain't seeing any real upgrades. As I said, in 2010 we had more companies, more mobile OSs and more people catered to. Today they seem to be chasing an even more narrow margin of users that they see as the 'future' and we older folks just accept it or stop using it. Just get the rapid progress and features back. We've been stuck in this stagnant rut since 2015 for crying out loud.
As for why Apple ditched PowerPC, there are plenty of theories/assumptions but none confirmed. Only Steve Jobs knew the answer and it died with him. If I had to guess, it was the last bit of the Sculley era and Steve wanted to get rid of everything he had a hand in (he took things really personal like)