I mean, when you put it like that, with hard facts and all, I can't really argue! Rose O'Rion was definitely 90s. Synnamon was 21st century I think? And maybe not technically a thief, but her stories were basically all techno heists. Maze Dumoir was also a spy rather than a thief, I think? But again pretty heist-y.
Prog 2250, with 4 out of 7 stories having female leads, is as positive a step as one can ask for in terms of balacning the sexes. (And yes, demon Jenny IS the lead Diabolik - at least, in that episode). So if it sounds like I was complaining, just tell me to shut up.