To be fair, I'd say they were completely complacent as a result of having been known to produce many elite-level combatants for years now. It's likely they haven't been attacked in a good, long time.
I mean... Jorōgumo are explicitly man-eating yōkai in a lot of works. So...
Nah, man, don't cast shade on one of the best X4 bosses. This man's far below that.