Are transport gliders used by modern armies?
No, there are no modern military glider forces, the Soviets kept an active glider force up until the early 60's before they retired them. All other military forces retired them before that because they really are not an effective delivery platform; they were inaccurate, often landing many miles off target, and had high rate of loss.

Gliders also tie up a large number of tow airplanes. Helicopters are much more capable, you can land troops on the tops of buildings or small clearings and are re-usable as well - gliders are generally non-recoverable as even if they are intact after landing they are often in inaccessible areas. Transport airplanes like C130s can land on very short, unprepared strips, or use the Low Altitude Parachute Extraction to deliver supplies without landing.