I’m not sure if I agree with offering the option to change a site setting in this context. In a community with a number of administrators, one doing housekeeping might choose this option without knowing why it was disabled or understanding the implications of enabling it.
I haven’t looked to see if there is a precedent for offering site settings changes in this way but it seems dangerous to allow settings to be changed as an aside to performing other tasks.
Potentially category deletion is disabled here for a similar reason, i.e. to encourage examining which topics are going to be deleted, though I don’t have a strong opinion about that. If that is true, perhaps the help text for the disabled delete button could be improved with a brief explanation of that.