AWS has never discontinued one of their services?

Not trolling, seriously asking (I don't use hyperscalers)

Ec2 classic networking is going away this month.

But that's ancient technology at this point.

As in "the second AWS product launched", and has been deprecated since 2013, which is around the time GCP became more than just App Engine.

Migration paths and assistance have been repeatedly sent out though - you’d have to literally not care about the system to have this impact you.

In fact the last ec2 classic instances are due to be retired... by today! Though I'd bet no one waited until the very last day to migrate :)

To the best of my knowledge, no. At least none of the AWS services I've used. They've deprecated support for some CAs and stuff, but that seems reasonable.

Not a full service but partial features like S3 Bittorrent support was removed.

There have been rare changes, like mandatory API version upgrades or some features being turned off. I do not recall anything being removed without a (better) replacement available beforehand, let alone entire simply services being turned off. See simpleDB as the canonical example of long term deprecation but continued availability.

Disclosure: long time Principal at AWS. The above is my own observation and opinion

Not that I'm aware of. They'd be fully justified in shutting down simpleDB since it hasn't had a feature update in over a decade, but they still keep it running. New accounts can't sign up for it and it only exists in the oldest regions.

They were going to retire old s3 path styles, but they changed their mind after customer feedback.

There was an ML service before sagemaker that you can't start using anymore but I believe it still works for existing customers

Yes: Amazon Sumerian.

That's exactly what you will do - invest time, and energy, a lot of both because AWS is a victim of its own legacy. Everything is an after-thought, everything is messy and its genuinely painful to use on anything except some basic UI driven functionality.

EC2 and S3 and some basic hosting stuff is fine but newer services such as AWS Glue, Athena etc are a horrendous mess for anything other than 101 type stuff.

They just retired EC2-Classic, one of the largest services they ever had

EC2-Classic was not its own service. It was a specific configuration of EC2. They retired that configuration by providing a full migration path into a new system that could be configured to perfectly replicate the old system if you wanted it to. Having gone through that migration myself with a bunch of services a long time ago, this isn't really a good example of a thing that AWS has killed off.