Spammers are better at SPF, DKIM, and DMARC than everyone else

I observe the same thing. However, that does mean that SPF and DKIM are useless (although DMARC probably is).

It is correct that SPF/DKIM does not really avoid spam, because spammers are not stupid and can read these standards like anyone else. However, before SPF/DKIM, I remember that I got a ton of phishing mails with FROM containing "support@paypal.com" or similar. Then came Bayes spam filtering, and that would move legitimate mail from Paypal to spam, because obviously, the phishing mails are quite similar.

This problem has pretty much vanished, because Paypal clearly denotes which IP addresses are allowed to send mails from that domain via SPF and the client can verify the mail via DKIM. For instance, Spamassassin makes sure that mails with correct DKIM and from paypal.com get a massively reduced spam score so that your Bayes filter will not move it to spam. This is hardcoded for a lot of domains (see *welcomelist_dkim.cf).