Why would it be baffling? Google’s spam filters have always been extremely low quality, even mistaking email generated by Google itself as spam. They simply don’t have the pride of craftsmanship to improve it.
In my world, spam was a true problem that was killing email. Truly killing it. You would have to create a new address every 6 months to stay ahead of the spam and have a functioning inbox. Very different world.
Gmail fixed that. And for me, there have been issues from time to time and in fact i am getting this very spam myself, but gmail permanently stopped the hordes for me in 2004.
Now, don’t get me started on their insane categorization choices.
Hardly. They didn't invent the tech. And they didn't perfect it. They haven't even tried. The evidence is in my Spam folder. I mean they mark messages they themselves originate as dangerous spam. "Dangerous" being their word, not mine. Screenshot from within the last hour:
I was in that earlier world too. They papered the problem over, a little. But no, they didn't fix it.
The return address is:
Google Alerts - googlealerts-noreply (at) google.com
Now, my impression is that all of the well-regarded email providers do a good job of handling spam—it's no longer a differentiator. (Although it might start to be again if Google has genuinely let their guard down.) Fastmail does a good job in my experience.