To the contrary, I find myself going through my spam folder to mark as NOT spam things like monthly newsletters from arts organizations. There are a bunch of concerts and plays I've sadly missed because of this. (Which I can only assume comes from people abusing the mark-as-spam button instead of properly unsubscribing, which sucks because it leads to other people missing the legitimate emails.)
Also things like invoices from Apple purchases (e.g. a paid app or AppleCare) show up in spam. Which isn't a biggie, but it does seem like bizarre that Gmail could ever get that wrong.
The number of spam messages I get in general, judging from what shows up in the Spam folder, varies wildly from week to week. Sometimes I'll get five over a two-week period, and then get a week where I receive about 15 per day.
I have manually marked a large amount of prior emails as spam, not sure how personalized the filters are.
GMail is not my primary email, though. I use it for Meetup.com, Slack, Steam, maybe one or two other things. A quick google search suggests that my email address does not appear on the internet. Maybe people not suffering from spam have similarly private addresses?
In fact, I actually miss occasionally useful stuff because half my incoming email gets classified as "promotions" and put in a separate folder I never check that was automatically created when I made the account. It's stuff like emails from humble bundle about new bundles and GOG about sales etc, so spam-adjacent
Everything goes to inbox now. I heavily pruned the number of lists I’m on and just deal with the spam-adjacent stuff as it comes in; better than missing something I need to know.
It would be interesting to know the cause. I have actually signed up to loads of dodgy websites over the years, my email has been "pwned" according to haveibeenpwned, etc. So there's nothing particular that I've been doing to shield myself from spam, but Google still catches it all perfectly.
But then again, I completely believe all the other people saying they _have_ had spam come through, so it remains a mystery as to why. Is it some specialized spam list of a certain group that know how to bypass the spam filter? Is it Google A/B testing their spam filter? Who knows.
Gmail's spam filtering was perfect before, so something is going on on my account (although not as dramatic as OP's).
So I do believe something has changed and I wish I was still in your situation.
I will say I’ve gotten what I consider spam from Experian where they claim to be MSAs (mandatory service announcements) on my account, but they’re clearly marketing, and I’ve just set up a rule to delete those. Done.
I also have gotten on political lists where unsubscribing doesn’t seem effective, so set up another rule to block those. Done.
Other than these 2 edge cases (that don’t seem to be blatant spam, just dark patterns), my inboxes are clean of spam.
I also have family (wife and two older sons) on Gmail, and haven’t heard them complain about spam.
One potential hint though: all of my Gmail comes through personal domains. So maybe these spam attempts are targeting gmail.com domain? I do have a gmail.com email, though, that gets forwarded to my personal domain one, and I still haven’t noticed any spam, FWIW.
1) 3 "legitimate" spams, i.e. unsolicited messages that the senders believe they should have sent. 3 of these. 2 via Constant Contact and 1 via Salesforce.
2) 1 random porn spam, via random spammer domain with valid SPF and DKIM.
3) 2 phishing scams with the same body arriving from random commercial domains without DKIM. These are almost certainly spread via malware/viruses/worms.
4) 1 Google promotion originating from Google with valid DKIM, because I mark all these as spam.
5) 2 phishing messages, with the phishing warning, that originated from gmail itself via HTTP. These are pwned google accounts or google accounts logged in on machines with malware (effectively, same thing).
6) 1 idiot Republican politician, via Mailchimp.
As a side topic, I've heard a lot of people say that the Gmail UI has changed and that it's unusable now. This is what mine looks like and I really like it, is it not how everyone else's looks too? https://imgur.com/a/3ahD0Ta