Hello, the latest version of exiftool gui is 5.16, I see that it is no longer maintained for several years, is it currently unreliable or even not working?
It depends upon the system. It is absolutely unusable on my Win10 system, but there are plenty of others here who seem to use it regularly. You'll have to try it and see.
But as an alternative, another user here made a new GUI. See hvdwolf's jExifToolGUI (https://exiftool.org/forum/index.php?topic=11355.0). You can also check the list on main page (https://exiftool.org/#related) for other alternatives.