Just look at JIRA... It's ubiquitous, cloud based, ugly and bad user experience. It's still successful.
If anything, I'd use Jira as an example of what enterprise software should be like! It's hardly perfect, but I s better than almost every other non-tech-oriented SaaS I've used.
Bugzilla is obviously very ugly (and directly out of the 1990s) but it does work pretty well and it's fairly logical to use.