These keen folk might not be so quickly disappointed, if they were not being told that they should be! Many of them are probably just delighted to be off the ground at all, and awesomely proud when they do it solo! Why spoil the mood for them?
I know many people who were very keen to learn to fly a floatplane. They would be equally disappointed with an attempt to take off a Chipmunk, as a C152 - from the water!
It's all a matter of your hopes and expectations at the beginning level.....
Step, I disagree. That's not how I remember it. No-one told me I should be disappointed; it came as a shock how awful the C150 was after the gliders I'd come from, and they (Ka4 and K13) were themselves a bit ponderous, especially in roll.
Richard Bach, in his marvelously inspirational book A Gift of Wings, encapsulated my feelings perfectly:
…. perhaps in the back of our minds, as we pushed the high-winged cabin into the sky, we thought ‘This isn’t like I hoped it would be, but if it’s flying I guess it will have to do’.