No, but it does add quite a bit of complexity, and if it's done correctly usually requires not just a database of timezones, but also when and how they've changed over the years.

Not supporting timezones is a valid design choice, but is so important and integral it should be the first item both mentioned by a library and used as criteria to decide whether it's a valid choice for those surveying libraries.

It's sort of like choosing a storage solution. Do you need persistent storage that can survive a reboot, or is something ephemeral that works only while powered good enough? Both have their places, but choosing the wrong one for your specific use case is usually very problematic.