Meanwhile your comments bury whatever substantive content they might hold under layers of emotional, accusatory garbage. Maybe get those feelings locked down a bit before posting?
If you have access to an experienced devops team who can securely maintain an nginx server with some proxy logic then maybe that's a possibility, but otherwise what other viable options are there? Wishing that JWT were more secure won't make it so, but neither will wishing that CORS were more flexible. And if it's a choice between subclassing the JWT handlers to provide a couple extra security checks vs trying to securely configure and maintain a whole extra proxy setup, then the former seems like the lesser of the evils.
[1]: https://docs.aws.amazon.com/cognito/latest/developerguide/am...
You have a responsibility to built trustworthy systems, and you get no pass on building with flawed components simply because you wish experts had made those components less flawed.