Initially the (justified) change gave you ~18 months to implement necessary changes. Seems feedback was negative regardless, so they modified it in a way so current usage remains unaffected.
Also: classic vs application load balancers - especially the health checks. That one drove me nuts for weeks!
AWS never seems to "deprecate" anything, but they do enjoy adding services which are very similar to other services but guaranteed to trip people (ie: me) up when it comes to the buried-in-the-documentation details.
"The EC2-Classic platform was introduced in the original release of Amazon EC2. If you created your AWS account after 2013-12-04, it does not support EC2-Classic."
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-clas...
That was 4 years after VPC was launched. So yes, while they do deprecate stuff on the rarest of occasions, they still give you much, much more time than GCP ever did.
Also, EC2-Classic is still available if you reach out to your TAM with a really good reason.
SimpleDB still works, it's not even deprecated or grandfathered to not accept new users. There is really nothing else you need to know about how AWS treats deprecation than that single example.
Deprecation is practically unheard of in AWS. If it does happen you can be damn sure it takes years to actually remove obsolete functionality and there is a fairly easy migration path to something of equivalent functionality.