I listened to the whole video, and the parent understands this better than you do. The video doesn't say that gliders are impossible, period. It says that slowly gliding down, without a heat shield, is impossible. As the parent noted, the Space Shuttle proved that quickly gliding down with a heat shield is possible and very realistic. The video doesn't claim anything to the contrary, of course.

It's a good and important point that the term "glider" needs to be qualified. But you failed to make this point.