This sentiment is pure poison. It is why we have such shit events all the time. It is why fighters pull out on a constant basis and many of them refuse to fight at anything less than 100%. This perception is why Floyd Mayweather will never have an exciting fight and why 5 million people will pay $100 for a crap PPV. It is the same reason why Aldo always pulls out, why GSP vs Silva never was and why us fans are blue balled on a weekly basis.
Fighters realize fans are idiots and that they will no longer support said fighters brand if the fighter takes a risky fight and loses. Said fighter will be labeled a can, even if he/she fights injured, on short notice, out of weight class as the majority of "UFC fans" will jump ship and no longer support the fighter. Many modern fighter is afraid to push themselves like a BJ Penn, like a Randy, and they take tailor made match ups, do PED's and cut massive amount of weight to gain an advantage and pad dat record.
This sentiment is the reason why guys like Julio Cesar Neves have records of 30-0 and lose at the first sign of mediocre competition. This perception has absolutely no place in this, the greatest sport in the world. This perception is for people who measure their worth by the number of their twitter followers, who measure quality of art by number of youtube views and who appreciate appearance over content.
The days of John Wayne are gone, the days where a man was measured by how many time he got up, not how many he has fallen down. We crucify those who give us what we actually want, those who give it their best effort and put their life on the line so that we may enjoy life more. The modern hero is now a ridiculously privileged man that has tits plastered onto his body above the actual woman that lives underprivileged so that her children may have a better life.
So no, BJ and Randy are both underrated and under appreciated. Everyone's day comes, and that window of dominance is usually very short owing the the highly evolving nature of the game. Both these competitors adapted and had years of dominance, taking on all comers and not afraid to take fights simply because there was a good chance they would lose. In fact, prime BJ Penn is probably the greatest P4P fighter the world has yet seen and sadly he has been crucified for the same reasons we celebrate GSP: he was willing to compete at a disadvantage.