Utility classes are problematic because they fail to group responsibilities with the data that supports them.
They are however extremely useful and I build them all the time as either permanent structures or as stepping stones during a more thorough refactor.
From a Clean Code perspective utility classes violate the Single Responsibility and the Open-Closed Principle. They have lots of reasons to change and are by design not extensible. They really should only exist during refactoring as intermediate cruft.
