Crouch teching seems to works pretty well in block strings, online shouldn’t factor at all as there is a 10 frame window, so if players can land 1-3 frame links often enough a 10 frame window should be trivial. Teching works but you can’t mash it out of it or hit it to early in the block string which is what most people seem to do as often times that is what many people do online and then the crouching light kick comes out or the tech just fails because they are still in block stun and then you get thrown. if something hits you are in block stun X frames then at +/- frame advantage and if you reversal that and your opponent is at negative frames you get thrown. You are trying to tech the throw so it needs to be delayed just a few frames after block stun and you have a full 10 frames that if your opponent throws you block and if your opponent decides to block or start attacking you have that covered. It is hard to time sometimes and just takes practice.
Though if you know a throw is coming such as empty jump or walk up and throw it is perhaps safer to stand up and try to throw them as that will eliminate the margin of error of you starting to early.
Everyone gets thrown at random times (IE opponent doesn’t have raging demon, shoryuken and two bars into ultra, dive kick, or other reasons not to crouch tech or throw) I don’t think I have ever watched a match where the players where not getting thrown but it doesn’t do much damage is mostly the set up after that are worry some.