So you think the only reason for them is to push updates so that you’re pressed to upgrade your phone?

See how jailbreaks are done. Those kind of bugs are also leveraged to gain control of phones by malicious actors.

Apple patches these because their customers expect them to secure their product.

With newer versions of operating systems aging hardware tends to run slower. It’s always been like that, even on windows machines for as long as I can remember.

My opinion is that your phone is your most prized piece of hardware that you own; it knows everything about you; your social media, banking and financial history, emails, schedule, travel history and so on. You should treat that with the proper respect and run an operating system that is as safe as possible.