It's almost invariably end users who suffer, not the "makers". And because of a human cognitive bias it doesn't matter that the middleboxes are wrong, if you get a new Chrome and it doesn't work you blame Chrome, you don't blame the middlebox that had been getting this wrong for five years.

Almost a year's work on TLS 1.3 was spent on working around problems with middleboxes. Because without that it would be impossible to deploy in practice. TLS 1.2 took years to deploy because so many middleboxes were incompatible and we had to wait for them to rust out.