TMobile is kicking old Android phones off their network in January because vendors have abandoned the hardware and they no longer get security updates. Android's model of forcing you to buy new hardware every few years to get security updates is broken. https://www.tmonews.com/2020/12/t-mobile-will-no-longer-support-devices-january/
Imagine if your ISP kicked your laptop off the Internet because Microsoft stopped providing it security updates. Imagine having to buy a new laptop every 2-3 years just so you could get updates. Phones are just small computers, they shouldn't have special rules.
@kyle In the early 2000s, I worked in a university NOC on a software that would identify PCs that were infected with malware (mostly Blaster at the time) and cut those machines off the network until the users had fixed them.
The relevant difference here is obviously the fact that the users had enough control over their systems to actually be able to fix the problem.