Create ECK Entity via Ajax
In your route you require CSRF token and your ajax call is missing the CSRF token.
Get a CSRF token from ur drupal site using url &quot;/session/token&quot; and send it with your Ajax request.
But is it wise to do it this way? i don't know.
For making ECK Entity with ajax Post i would use REST resource or make a custom REST resource with basic_auth or cookie authentication, that way you wont need a CSRF Token.