The only real issue for email today is deliverability. That's getting worse, according to reports from people who have not had a stable verified public IP address for decades.
Except when spam filtering effects deliverability and results in mail the recipient wants to receive going to a spam folder, with no way for the recipient to change the filter. For example, I have a friend who has his own domain based on his surname and his mail from that domain goes to Gmail's spam folder even when the recipient marks it as "Not spam".
Well, that train of thought went downhill pretty fast.
Could it be perhaps that mail is becoming undeliverable precisely because effective anti-spam is so burdensome that only major players can eat the cost, while pushing massive externalities to every other mail provider?
When the "Unsubscribe" feature fails (about 10% of the time in my experience), then those emails are legitimately spam. None of the spam solutions work for those emails.
If spam is a problem for you in 2022, you have a crappy email provider.
If you sign up for something (e.g. by purchasing goods from a legitimate store), those will virtually never be classified as spam. The reality is that it is hard to get off those lists - a lot of them have an "Unsubscribe" link that purports to get you off their list, but do not actually do so.
If you have a provider that is classifying them as spam, then you have a crappy provider.
I consider the unsubscribe button a courtesy, but the “mark spam” button is the real unsubscribe link. I wish modern email systems had a button which did both - “unsubscribe, and mark any future email from this domain as spam”.
The spam has now filled up my Google storage quota, and I can’t use Google docs with that account any more. (I’ll probably just backup & delete all email in that mail box soon to restore the account)
If gmail’s spam detection is “crappy”, I’m very curious who you consider “good”.
FWIW, I run rspamd for half a dozen users. It correctly classifies upwards of 6000 spam messages, and ~300 non-spam messages per day. A dozen or so false positives get through per week, and I haven't seen a false negative in at least a year.
I'm probably more annoyed by spam than most people are, but it has barely occupied any part of my brain in a decade.
I guess my original comment should have been more specific. Spam detection is a solved problem in 2022, and has been for many years. That some providers implement it poorly is, well, crappy.