Time was when we used to teach S turns, both for final approach and
launch failures, and this was fine in slow, wooden open cockpit gliders.
We also taught slipping. Pitching nose down 10 or even 20 degrees in
a T21 when side slipping was not a problem, doing the same in a
modern glass glider certainly is, especially when you stop the slip, the
glider will accelerate rapidly, unlike the T21 which did not understand
acceleration.
The difference is between what we teach, which has very little do do
with what is possible to do. Modern teaching tends towards getting the
circuit right so that the "emergency" procedures are not needed.
Modern airbrakes tend to be so good that even if you get it wrong they
are all that is needed.
S turns and sideslips are perfectly valid solutions, just not something
you want to teach a low hours pilot, concentrating on getting the
circuit right and effective use of airbrake is much safer.
I still fly a T21 and sideslip a lot. I sideslip very little in glass ships
as
proper use of airbrake, at the correct speed, is much more effective.