An important adage of Taijiquan is not to meet force with force which is actually derived from the true rule which is Bu Dui Bu Ding, don't break contact - reject brute force.
The important word here is "brute". It is important to understand that without the use of force we would not be able to stand up, let alone move. Thus the idea that a Tai Chi master can perform any defensive or offensive manoeuvre without the application of any force at all is palpable nonsense.
However this does not stop many so called masters and their acolytes from claiming this ability. Any independent investigation of this phenomena inevitably reveals the lie. But I digress.
When an attack is made the defender has a variety of options to respond
The method we use in Taijiquan contains elements of all the above although methods 1 and 2 are informed by Bu Dui Bu Ding. We train to absorb attacks using both the arms and the body. When direct contact is made we do not tense up but move with the initial contact and then stick to it to prevent secondary follow up attacks.
Novice practictioners do not have this ability and hence perform the applications in the simplistic blocking manner. The methods look the same as in every other Martial Art however the method of application is very different when performed correctly. However most students seem to be unable to unwilling to change from the basic method.
It is often said that there are no advanced techniqques in the Martial Arts but this is not the case. There are many techniques that require an advanced level of skill and highly trained power that only the experienced advanced practitioner may perform. These advanced techniques are often invisible to the external obsever because they involve subtle weight shifts, slight body and arm twists, correct positioning of all elements of the body and precise timing based upon heightened trained sensitivity.
Many practitioners give up after a couple of years of training because they have not got it. Some are frustrated because the applications do not work for them in any other context other than in the training situation. The problem is translating the application from a safe known sceanrio to the unknown adrenaline charged free fighting situation. Most cannot handle the stress of the fight situation and tense up, hence they are more suited to a martial art that enables them to tense up and block with force.
A blocking manoeuvre that requires force is susceptible to feints but the Taiji method of sensitive detection and reaction to what is actually happening rather than what is apparent is the key to mastery of Taijiquan.
When junior practitioners state that some method or technique in Taijiquan does not work or is susceptible to this or that they really have not understood or mastered this aspect of the art.