Good players will know what attacks put them at a frame advantage. For example… Bison’s LK scissors. Blocking the scissors technically doesn’t put bison at a frame advantage, however it does guarantee that they will be at 0 frame advantage (meaning that they know for a fact that you had no chance to already start an attack.). They KNOW that you’re at equal frame advantage. Bison’s crouching short comes out in 3 frames. Bison’s crouching short will win that exchange. If you try to throw or crouch tech you will get hit for free. Not only will you get hit, but you’ll be COUNTER hit. A counter hit is when the opponent hits you while in the process of trying to attack. If you try to throw you’ll be in throw animation when the opponent hits you. If you try to crouch tech you’ll be in the crouching short animation when the opponent hits you. A counter hit not only grants the opponent more hit stun than they’d usually get for that hit. It also grants more damage.
So, what do you have that beats bison’s crouching short? Nothing. You could gamble a super or an ultra if you want to (probably) get hit for free. You could try to teleport, but again that’s an insane risk as you’ll either be caught out of it, hit with a standing roundhouse, or scissors.
So, what do you do? Block. That’s all. If you do anything else you will lose on the exchange and the opponent will STILL be in your face. A big part of Dhalsim’s game is staying patient, blocking. The opponent will get impatient and try to tick throw you, or just throw you. You have to get good at teching throws, this is something that will come with experience. But, if you try to crouch tech at the wrong time, or too much… You’re simply going to lose 1/5th - 1/2 your life. You have to block and wait for an opportunity. Either the opponent will jump allowing you to short slide -> teleport away, they’ll throw allowing you to tech it and create distance and remove frame advantage, or they’ll get pushed back by their own attacks far enough for you to b.lk, b.MK and have the option to cancel b.MK into into either teleport or fp yoga fire.
Crouch teching as SimSim mentioned is important to be able to do. You hold down+back and hit LP+LK a split second AFTER the opponent hits you. You do this for every hit in the opponent’s blockstring as long as they’re close enough to throw you. Once you’re pushed out of throw range STOP DOING IT. If an opponent hits you, then goes to throw you right away you’ll tech their throw. If the opponent hits you and tries to delay a moment then throw you, you’ll hit them with a crouching short. If the opponent delays for a moment and then does scissors kicks… well… you’re going to get hit and knocked down. This is the danger of this method of crouch teching.