The text fields on the sign-up form [0] are unlabeled, the submit button ("Register") doesn't visually show keyboard focus, and almost nothing has sufficient color contrast; that doesn't bode well for the actual player's accessibility. Also, the <form> element has a completely unnecessary role="form" ARIA attribute which suggests accessibility has crossed someone's mind but also that it's likely errors of consequence have been or will be made.

[0] https://play.pocketcasts.com/users/sign_up