I believe one is coming to the dojo to be frustrated and NOT to be comfortable. Comfortable training is useless. With comfortable training, students become lazy and don't develop a basic habit of stealing techniques from instructor (by variety of ways). Instead, they are only waiting passively for help like a sheep.
Later on, when time comes to develop the applications facing sophisticated attacks, they have not skills ready to find instant solution. And as in aikido you don't have second chance, from martial point of view, the result is a ‘death'.
I think the problem here is that people of this era believe that as students of anything, we will become accomplished. Just like going to a university means we end up with a degree, we think that by going to dojo we automatically are going to 'get' aikido. By paying sensei, you expect him to transmit his knowledge to you.
You may 'get' aikido. Some people better than others. Some quicker than others. Frustration along the way is inevitable. Learning to overcome jammers is knowledge. Certainly it would really help to be able to fail now in the dojo, than outside when you're truly tested. But if you never learn... then part of it is your problem.
Sensei can guide us, but its our responsibility to learn.