My last gig was as a CIO in a fairly large organization and we had stringent infosec requirements due to the industry we were in. Old operating systems and software are absolutely an issue, although it still doesn’t stop some companies from running them.
Most of the malware going around exploits patched vulnerabilities. It literally takes seconds and not exactly a high skill level to compromise a machine that’s missing security updates. Regular patching is without a doubt one of the best controls you can have in place. The other big issue was social engineering. If you don’t effectively tackle those two things it doesn’t matter what else you do because you will be breached.
Besides that, you’re mostly right. We were all over the security updates but didn’t care for other upgrades because they introduce instability. It’s the last thing you want with thousands of endpoints and a bunch of shitty enterprise apps. Run it until the wheels fall off or it’s approaching EOL for security updates.