I ran into a site like this recently. Honestly, I think it's great because you can tell what action you need to take to resolve the error. Clear cookies? Come back later? They're actually out of business? The stack trace reveals all.

I enjoy how transparent client-side apps are these days. I remember trying to order something from an online store, and the "submit" button wouldn't work because some third-party license key wouldn't validate (I think it was to load a map to show your own address?), and that error stopped the actual sending of the HTTP request to submit an order. I patched that out and submitted my order. Easier than finding their email address and waiting a week for their contractors to fix it.