Most are taught forms and Zhanzhuang and expected to find this unattainable feeling. Actually using it to fight is so far in the future that you may as well forget about it.
Shifu said; "Song? What is Song? Do the form with a brick in each hand every day. Then do it without. That's Song." Furthermore, having studied with five or six masters [of different Taiji styles] in different parts of China, another thing became apparent; the whole form was never taught by the master, sometimes not even partially. It was doing repetitions of "Yunshou", "Yema Fenzhong", "Danbian" and other "postures" over and over again with footwork, plus other Gongli training. There was also specific Neigong training to connect the body and mind and learn how to Fajin. Also, there was fighting! Linking the movements together into a form was more of an afterthought to help you remember the whole curriculum and give you something to practise when you were lazy or demonstrate the art to others.
Tuishou and Sanshou was taught from early on but was basically getting your arse kicked all the time until your Gongli started achieving results. Shifu loves saying; "I'm not the Shifu. THIS is the Shifu!" *Insert strike, kick, Qinna, throw etc.* You learn to protect your balls at all times quite quickly! Shifu says that if his students aren't exhibiting some internal power after several months of training that he is failing as a teacher.
I began studying his foundation training, which is the same regardless of which art students decide to learn from him, and wanted to get out of Taiji, which seemed like a hopeless cause. Shifu, bless his heart, began teaching me Xinyiliuhequan and even some Baguazhang and other arts (he likes to mix things). After several months I realised that they are all variations upon the same thing (seeing and getting my arse kicked by his effective Taiji helped too) and that what really matters is which one you like to train. I enquired more about his Taijiquan and he said that he wasn't surprised. "I knew that you'd come back to Taijiquan," he said. I asked him why he still let me go around in a circle. "Everyone that studied Taijiquan and then came to study from me was the same. You are all frustrated and think that the problem is with Taijiquan. In fact, it is no more difficult, complicated or less effective than any of those other arts. You all needed to come to the conclusion yourself. Just hearing it from someone else isn't enough."
And so it is that I'm back onboard with Taijiquan, but also improving my Sanda (or some semblance of it) and slowly learning some other stuff to complement it. For any of you on the fence, think carefully about the way you are being taught and whether you have actually attained any Gongfu or not. If it has been years and you are still as weak and useless at fighting as you always were, it may be time for a change (whether it's still Taiji or not will depend on the quality of teacher you find). For me it is exactly as Shifu said it would be before I started studying from him; "I will help you to build an engine. If you want to put it back into your Taiji or any other art, that is up to you." Good luck everyone and keep training hard (or start, you lazy fucking bastard!).
In conclusion, the "feeling" is not found by searching for it, but developed over time through hard, sometimes painful work, then brought back into the form. It is NOT found by doing an empty form ad infinitum. Imagining that you are doing hard work and fighting is not enough!
But, shit, you reminded me that I forgot to ask him about the Dantian today..