depends on how many other apps, especially the native ones that won't get updated anymore, you are using.
for instance, at least as far as i understand, just receiving an iMessage from some stranger without the need for you to even click on it, has been enough at one point to corrupt your macOS or iOS device.
of course this has long been patched, but you never know if, or when someone else found some other loop-holes in one of your apps that don't get updated anymore on your unsupported system.
personally, i still think that you should be pretty safe if you are using common sense most of the time, but there is still some possibility that your system could be corrupted in some rare cases even if you did nothing wrong, or even nothing at all.
but of course even up to date systems are not immune to such newly surfaced zero day exploits either. they are usually just not exploitable in that specific manner for as long.
but there are also some recently fixed exploits are said to have been abused for more than 10 years before they had been discovered by some of the good guys.
