Apologize for your experience. Where did you hear that this was an issue with Catalina? Having that context will help me check if this is indeed an issue that we are aware of and the team is investigating.
I am on Mac 10.13, I tried installing and using the Poppins family of fonts at my end and I did not have any issues.
Can you check if you are logged into XD with the same account that you use for Adobe Fonts? Also try logging out and logging back into the Creative Cloud.
If nothing helps, send me your Adobe ID, location, and phone number over a private message. I can arrange for a tech support person to reach out to you for investigation. If you are in a rush, you can contact the team directly https://adobe.ly/2WYE62m Use the chat button on the page to get started.