I've been re-implementing Remedy functionality for a telecom operator around year 2000. They decided to go with custom software because Remedy was horrible. I wonder what kind of horribility it is now, 20 years later.
And we still have to use ITSM systems that look and feel almost exactly the same like 20 years ago. How it's possible, the ideas behind these tools are not exactly rocket science, simple ticket tracking with some standardized data structure and relationships - nothing that you couldn't put together in a month. I wonder why companies even buy these tools, probably you could have much better system developed for you and your specific needs for 10% of what it costs to buy certified ITSM system.