[leptons]

Apple switched to ARM CPUs. Your 2008 MBP now has an expiration date, where it will not be capable of any more OS updates after a certain date. All Intel Macs will not be supported after a certain date. We don't know what date that is yet, but it is coming.

[gambiting]

It already didn't get any "official" updates for years now but there is a community porting latest versions of MacOS to it, that's how I'm running Catalina. Besides, even with the ARM chips coming, it doesn't look like Intel macs will disappear straight away, x86-compatible MacOS will be around for years and years, if no for any other reason than that currently sold Intel macs will still be getting updates. And besides, it's a 2008 machine - if I only get a couple more years out of it then that's still great.