I run an email server with no specific spam filter. Sometimes I get spam. Then I add a filter on my end to delete it and move on. It's nowhere near as bad as people proclaim. Neither is deliverability, for that matter, even after I forgot to set an SPF record and some random internet server sent a bunch of spam on my behalf (which I know because I got the bounces).
You have a dirt path to your house and are therefore convinced the interstate highway system should allow direct residential driveways.
Gmail processes 376 billion emails per day. At that volume, even 0.1% spam getting through is 376 million messages. However, we're not talking about 0.1%, but 45.6% of email being spam globally. For Gmail, that's 171 billion spam messages daily. Congrats that your private server works at your scale. It's completely irrelevant, and only works because bad actors don't care about it.
Imagine though, if we even accepted spam culturally and handled it individually, as per your solution. That would mean spam can get through with brute force, which it can't right now, meaning that 45.6% would probably explode closer to 90%, 95%, or more overnight. It's only manageable at 45.6% for you because Gmail's spam filters are working overtime harming the economics.