I'm skilled with mail servers too, I've been running my own for years 🤓
Luckily the majority of spammers are amateurs and never bother to configure and run their own servers; when they do, it's poorly configured. Often they use sendgrid or other big services. Indeed, we can't solve the spam problem at 100%, but if we can minimize it then it's a step forward.
Nice to meet a fellow postmaster. :)