Knowing all your players current stats, feats, and items is a pretty high bar for a casual DM.
But also, if some of your player's characters can make the roll and some can't, I'd say it feels worse to say off that bat, "Roll a WIS save, except you Phil, you fail." That will feel more like getting targeted than your build just not being suited to the current situation when you roll well and still fail.
A truly horrifying prospect.