Earlier quoted context omitted.
This is exactly why GDPR exists. What you are describing is illegal in the EU. Sending marketing communication requires clear opt in consent.
I just had this experience today. The problem is that at least in the States the regulation is ambiguous enough to be abused to hell and back. Unsubscribe in the States could mean “Unsubscribe from all” or “Unsubscribe from 1 of 20” or it could mean “unsubscribe from all now, but we will arbitrarily resign you up for some new newsletter whenever we feel like it”. I got a spam email today from some no name dropshipper…
The LinkedIn way.