Seems they are the disease not the cure
Lately I've also been getting a lot from compromised MS365 accounts.
It seems insane that gmail doesnt provide a way to automatically send a mail (eg based on domain, keywords, etc) to spam. I know theres block sender but for example aliexpress uses a different name for every email so that's useless.
What this is called is survivorship bias. The question I would ask is how much mail are you not seeing at all because it's dropped at the edge first thing because it's IP block listed?
Next, how much spam are you seeing from them because they and Google are the largest providers on Earth? Kind of like selecting a random person from the population in the US and going "look, it's a white guy". Yea, that's how statistics works.
Lastly, because the are good at blocking spam at the edge, then that's the last bastion of attack for spammers to put their efforts in if they want any return at all.
Self-hosting allows me to use a different receiving address for each entity I contact, so I know exactly who put me on spam lists and if it gets bad I can route that address to the garbage bin.