I'd say it's not that they don't want to be in the pro apps business per se, so much as they don't want to be a software contractor for big studios, which is what most pro app companies inevitably become. Apple wanted to make big changes, but mostly, big studios / production houses don't want big changes.
Avid probably couldn't make a radically different Media Composer even if they wanted. The risk of alienating current customers is too great, and the resources required to maintain multiple products targeted to the same market are too many.
... and focused more on features that are useful advanced amateurs
I actually don't think this is quite right. I'll quote Gary Adcock's Macworld review:
"Most of the features introduced in FCP X are welcome and badly needed. Some are long overdue. Still, others are positively jarring and require a change in mindset to appreciate."
There is no doubt that Apple made it unusable for high-end pros (for the time being, at least) but I feel they also added many things that high-end pros would have really appreciated, had they been able to use it seriously. So it's not quite as simple as "amatueurs only" (even if you're talking about advanced amateurs.)
Avid probably couldn't make a radically different Media Composer even if they wanted. The risk of alienating current customers is too great, and the resources required to maintain multiple products targeted to the same market are too many.