It's ceratinly possible to fly most standard planes on a 5 channel non-computer Tx. 'Back in the day' when i started out anything more than 4 channel was a very expensive luxury, computer Tx's were unheard of, and even reversing switches hadn't made an appearance (you got left and right hand rotation servos).
So the problem can be worked around if you are determined, but all these modern features certainly make everything much easier.