I periodically see sites broken in Firefox until I turn off uBlock and/or Privacy Badger - including issues with paying like you describe. But I've always assumed that the same would happen in Chrome if I had the same extensions installed there. This seems more like 'locking out people with adblockers' than 'locking out Firefox', even if there's substantial overlap.
It's distressingly common for JS developers to just throw something like "t.track('payment')" in the onclick handler for the last button (or every button) in a payment flow, where "t" is some analytics package you've blocked. No exception handling, of course, so when the analytics package isn't loaded, nothing happens when you click the button. If you're lucky, there will be a console message logged saying something like "unable to call method track on undefined".
