MusicXML has its uses, but it isn’t particularly useful to me personally. I work with lots of modern scores with aleatoric notation etc. MusicXML has no good way of interpreting anything like that - if is something very traditional (classical era etc) or film music or something more commercial then it can be very helpful of course. But if I receive a score that is chock full of extended techniques, and very little traditional notation, MusicXML is really of limited value in interpreting it.
I find Dorico note entry just fine, and before Dorico I worked in Musicator, then Finale, then Sibelius.
Certainly I think it is important for Steinberg to make a big push in education. Like you and dankreider I agree about people tending to stick with the apps they used in college.
Finale I think is secure for the foreseeable future in terms of its core base - too many publishing companies use it as the standard, too many established composers are so used to it that they wouldn’t even consider using anything else. However, given the way things have been, I am expecting Sibelius to be discontinued in ~5 years time. Avid doesn’t really seem to care about the product, and the Sibelius base isn’t as solid as Finale’s. If Avid continues to show that they don’t care by forcing yearly subscriptions in exchange for a few token surface features, users are not likely to stick with it in the long term and will jump ship (mainly to Dorico, I should think).
For me, the justification to composers who use Sibelius is really this: Sibelius is probably not going to exist a decade from now (my own opinion, but I think it has basis in reality). If you write a piece in 5 years that is your magnum opus, and someone 5 years later really wants to perform it but wants an instrument swapped or some other minor changes, what do you do? If you stuck it out with Sibelius too long, and the product is discontinued and can no longer run on a modern computer, you re-engrave it from scratch. What should be an hour of work becomes days of note entry and proofreading. Who wants to be stuck with that?