What happens if you have tables with helper data in them? Lists of states? ZIP code data. Stuff like that. Those aren't system tables, but you also don't want to delete that info. Whatever way works for you is the best way. :)

I have something similar. I exclude system tables AND certain named table that I don't want to delete data from.

Yeah you could name your own tables with a prefix or suffix to automatically avoid those in a loop.