Filtering incoming spam, while not 100% correct, is a pretty straightforward thing to do. Use DNSBL and other lists from spamhaus and it takes care of 90+% of the problem. Incoming spam has not been a huge issue for me, but when people try to send mail to someone in M365 cloud or to Gsuite and they just decide that your server isn't important enough they just block you out and that's it. Trying to circumvent that takes a ton of time and effort and while it can be done it's a huge pain in the rear. And trying to fight your way trough the 1st tier support to someone who actually understands the problem and attempts to fix that while you customers are complaining that "problem with email" is actually affecting on their income is the part I'll happily leave behind.

I'll set up a couple of new VPS servers to host my personal and friends emails, but if they complain that the service I'm paying from my personal pocket isn't what they're after then they're free to switch into whatever they like. And as infrastructure for that is something like 100€/year I'll happily pay it by myself so that no one has an option to say 'I paid for this so you need to fix it' anymore. On commercial case that's obviously not an option and I've had my share of running a business in a very hostile environment.