<shrug>
For what its worth, I've always found it easiest to teach gliding performance by remembering that lift and drag are a merely a 'convenient' way of resolving the total aerodynamic reaction.
If we take thrust to be zero (since we're talking gliders) that then leaves us rather nicely with two forces; Weight and Total Aerodynamic Reaction. If they are equal and opposite then the flight path is constant; we are in a steady glide.
This could be a house brick falling at terminal velocity, or a theoretically perfect glider flying level.
Gliding range is all about how that total aerodynamic reaction is provided. Since drag is defined as parallel to the flight path, and lift perpendicular, our house brick clearly must have an L/D ratio of zero.. entirely reasonable. Likewise, our perfect glider must have an infinite L/D ratio, again entirely reasonable (if not quite achieveable in reality).
Gliding endurance is all about the ratio between weight and the vector addition of CL and CD. If an object can generate a big total aerodynamic force from a small airspeed then its weight will be balanced out with a lower terminal velocity, so its 'gliding' endurance is larger. e.g. a lead ball versus a feather.
So, I'm with DFC in that no drag = no descent.
But I think you are both talking slightly at cross purpose regarding gliding because you're swapping interchangeably between considerations of range and endurance.
Adding drag decreases range but increases endurance (assuming of course that the optimum speed is flown in each case), this is best understood by reducto ad absurdum; deploy an infinitely large parachute... what happens? Glide path tends to vertical, endurance tends to infinite.
(All of which diverges someone from original topic... but so what... I'm bored)
regards
pb