If a user wants to connect a third party app to Strava to access THEIR DATA, they should be allowed to and it’s their responsibility to read the other website terms of service and privacy.
You can download a data export and upload it to whatever service you wish. You're not necessarily entitled to make Strava do that data sharing for you, though.
It's still a pretty shitty move from Strava's side. I wonder what AI model they're training (or other companies were training) with the data now no longer easily accessible through the API.
Nonsense. The user did intervene: with an OAuth 2 flow. The user doesn't intervene with every API call or database query a data export makes.
What you're really getting at is "the user can't authorize someone else to look at their data". That's like a hospital saying your spouse can't get an update on your condition in the emergency room because you didn't hand the documents to them yourself.
It's certainly well within their right to change this rule and cut off API access, but I suspect a lot of people are going to tell them to go screw themselves.