Clarification question, since I'm curious. I don't believe I've ever received a spam message from a Gmail domain on any of my email addresses, some of which are posted publicly (support@etc.com addresses for businesses). I do see lots of phishing attempts from Gmail addresses attempting to impersonate Facebook ad support and similar types of very loosely targeted low-effort phishing. Am I an outlier, or are you seeing actual spam coming from Gmail addresses? To be clear, I'm calling spam unrequested marketing and nigerien prince type scams. I'm just curious, since that doesn't align with my experience at all.
Not general marketing emails, rather loosely targeted phishing or pointless spam email (one liners which I am not sure what point they serve other than nuisance) from leaked email addresses.
The benefit of having a custom domain is that I provide distinct email aliases to each website, which I keep track of, so I know which website leaked an address (and I also see those email aliases in the failed login attempts to my mail servers).
That also allows me to severe my relationship with a website if they start spamming me, so that may also create a selection bias since I am unaffected by the sort of spam resulting from the same email address being leaked to data brokers and used for marketing, because I delete the alias at the first offense. So I get mostly hit by websites that got hacked.
