First of all, Chun is by far NOT the worst character in the game.
Your problem is, in all SF2 games, throws take 1 frame, opposed to 3 or 4 frames in sf4. The opponents are tick throwing you which is sort of also in sf4, but the difference is it is a lot easier to escape in sf4 because of the slower start up. In sf4 you can jump away from throws if you know they are coming or you can use reversal the throw. In sf4 the time where you can input a move for it to be a reversal is a lot larger, so it is easier to escape. You can read up about ssf2thdr tick throws here - http://www.eventhubs.com/guides/2009/jan/14/throwing-ticks-reversals-super-street-fighter-2-turbo-hd-remix/
So the best ways to escape a throw trap in sf2 is to land a reversal. You can see a list of all reversals here- http://www.eventhubs.com/guides/2009/jan/14/reversals-super-street-fighter-2-turbo-hd-remix/
As you can see you will use chun li’s upkicks to beat any throw or hit. This is very hard to time perfectly so it will take a lot of practice to get down. You can also throw the opponent yourself, if you opponent doesn’t make it a true tick throw setup (you have time between when the hit you and when they throw you) you can throw them. Also if you throw them the same frame they throw you during a trap, you have a 50/50 chance of throwing them yourself, and if you throw a little to late you will still soften most throw and make the trap harder for them.
Also chun li has a trap herself she can use, use her :df::hk: move to cross you opponent up as they get up, if they get hit, they fall to the ground and you can do it again. If they block it, you can throw them and then repeat. Its a very hard trap to get out of.
And you forgot the list balrog’s throw trap, which is by far the most deadly. He will try to cross under you or fake you out and not cross under you, so block correctly and then use a reversal, or just try a reversal right away.