Orchestral Excerpt = Poorly Orchestrated?

Allow me to reflect on my most recent yet only marginally successful attempts to hack through a few of the orchestral excerpts I've been putting off learning for, oh, let's see here, my entire existence:

I've heard it said about orchestral excerpts for tuba that either anyone can play them or no one can play them. It's funny because its true. What does it mean when something that "anyone can play" (mind you I am talking figuratively here) has become a standard excerpt? Most typically, it's because it's important thematically AND it's famous. The Meistersinger excerpt would be exhibit A; not the most demanding thing in the world, but where else in the entire repertoire (let alone in such a famous piece) does the tuba play the entire tune?

On the other hand, the mechanism by which an excerpt from a more obscure piece becomes a staple of the audition circuit should serve as a warning to all of us wannabe composers. The only way an excerpt from a second rate piece becomes standard is if it's so hard that even the best orchestral players in the world have to practice it for years to get it right. In other words, such excerpts represent things you really shouldn't write (or at least not with the expectation of it being played correctly by mortals).

Now comes the part where I get to whine (eat your hearts out, singers). Want to know how NOT to write for tuba? Just take a look at the Fountains of Rome excerpt. If an undergraduate comp student brought something like that to their lesson, they'd be buried beneath a heap of the usual criticisms. (although come to think of it, I can't say it's not idiomatic; I guess that makes it more "idealistic" than "unrealistic?" It's damn near impossible to play in any case.)

As of today, my new goal as an orchestral composer is that if in the unlikely event anything I ever write gets called on an audition, that it be for the first reason and not the second reason (i.e. because it's famous and catchy, NOT because only 1% of everyone ever to play that instrument can even imagine making it happen). Meanwhile, pardon the clatter while I continue to fluff and cack my way through Fountains a la the other 99%