DKIM, DMARC, SPF, rDNS/PTR, EHLO... all correct and verified in the email "original source," BY GOOGLE. Still goes to SPAM folder because **** you, apparently. I hate Google.
Oh, there have been plenty. The issue though is the classic "make a better standard, and now you have N+1 standards".
Everything is wrong with SMTP. It's still in use because it's supported everywhere. Anything that wants to replace it either needs to entirely replace it in one fell swoop, or it needs to be backwards compatible.
The result is that occasionally a new thing comes up, a handful of people try it but there isn't critical mass to make other features really useful so it fades.