I agree with all your points. I’m aware of the time based individual account suspensions which are useful.
The points being made would also be points against automatically permanently banning (with no alternative choice) registration and last used ip when flagging a post as spam and deleting the user + content.
IMO each individual spam prevention feature, is generally easily defeatable by itself. Each feature has different scenarios that suit it better. Sometimes they are just a short temporary fix that can be used while a better solution is implemented. It is better to have multiple tools to fight spam (both prevention and clean up). Also that, spam defenses are only as strong as the weakest link.
If a spammer is running 100 accounts on the same IP (not the same as the unique registration IPs). A moderator who searched accounts that use that IP are in for a lot of manual work to simply stop them from posting despite how easy it is to identify them. Manually navigating to all 100 of the user admin pages, selecting suspend, select duration, input reason/email, submit. Much slower if wanting to delete these spam users + content also.
There is the bulk account deletion feature when you click on a user IP on their admin page. It is more heavy handed than just preventing posts on banned IPs. It rarely works for me though, just runs forever without deletions being processed.