EC2 Classic was essentially deprecated back in 2013, whether it was said as such at the time or not. 8+ years is an incredibly long sunset period, especially compared to AWS’s competitors.
> All AWS accounts created after December 4, 2013 are already VPC-only, unless EC2-Classic was enabled as a result of a support request.
There were announcements made at the time, but I don't remember if they explicitly called it a deprecated product at the time (hence why I hedged my wording in GP comment).