Is that good, though? I can't count the number of times where the failure mode of a JS submit was an endless spinner, a confusing or ambiguous message that does

Is that good, though? I can't count the number of times where the failure mode of a JS submit was an endless spinner, a confusing or ambiguous message that doesn't delineate between "invalid input" and ""unexpected server error", or worse, no indication of the failure at all. As rough as the experience of being taken to an error page is, I think it's often both more obvious (for users) and easier to get right without thinking too hard about it (for developers).