iPad 5th gen is compatible with Fitness App? I get message in App Store that it isn’t.

If you're talking about Apple Fitness +, as per the support article that led you here, iPad 5th generation running the latest iPadOS version IS compatible. Obviously you need an Apple Watch series 3 or later paired with your iPad.

Re-read that support article, and/or these ones:

Are you in a country where Fitness+ is already available?. Check it here:--> Availability of Apple MediaServices

Should be this case, read this article:--> Get Apple Fitness+ - Apple Support

Regards

Giulio

You are welcome !

Unfortunately we, just users like you, are not aware of Apple decisions/plans.

If you'd like, please submit your request/suggestion to Apple directly, using this link:--> Apple – Product Feedback

Regards and best of luck.

Giulio