I'm in the same boat. Since November, I will go 1-2 days with no spam, and then, whammo, in the space of a few seconds I get 4 or 10 or 15. I am mostly an iOS user, and I have not found a way using the Mail app in iOS to forward the emails to
spam@me.com as an attachment. I kept my Google account and I'll give Apple some time to address this before I switch, but I wish we had even a "yah we are working on it" note from them. It is not apparent that they are. If they improve, great, I'll stay with iCloud mail. If they do not improve, either because they cannot or will not, then I'll go back to Gmail.
Question: if I set up rules on iCloud.com, do those rules run before the email is sent to my iPad or iPhone?