Luc, I think you raised a very interesting point. I have heard so often from teachers that we would never get to O Sensei's level or even to the level of such and such master.
Therefore, what is the point doing it? In all disciplines (science, sports and so on...) we build on top of our seniors, we still their knowledge and go beyond. Why would the way of harmony be any different?
Of course arrogance is to be avoided at all costs but IM
HO too much modesty can aslo prevent progress. I have seen many students doubting so much of their own skills that they simply regressed!
Of course, we may also talk about the kind of people who hide beind fake modesty just to hear people tell them "no man! you're so good!"... They also very often give you lectures on humility (my humility is bigger than yours)...
When I am asked by people
"You're doing Aikido, are you any good?"
I generally answer, "yes I am pretty good at Aikido (I wouldn't have spent so many years doing it if I wasn't improving would I?) but I still many many miles to go!" Might sound arrogant but at least my answer is honnest.