I never actually put any serious effort into using MuseScore myself before the changes, so I can't comment from extensive personal experience.

But as a musician, I did use scores written by someone in MuseScore, as well as ones written in Sibelius. And I could always tell when it was MuseScore. I'm sure it was possible to write good looking scores in MuseScore 2, but it clearly did not make it easy. The scores were obviously inferior in terms of layout and design compared to those produced in Sibelius. Basic things like spaces between notes not being the right proportion, or dynamic markings appearing as plain italic text instead of the usual bold dynamics would be wrong in MuseScore far more often than in Sibelius.

As a general rule, a good UX should:

1. Make it very, very easy to do (or discover how to do) the most common basic things, and should result in them being done in the way a user expects
2. Not slow down a power user from accomplishing basic tasks at speed
3. Allow easy discovery of and access to less common tasks

A lot of designed-by-software-engineer FOSS applications do a good job of 2 and an ok job of 3, but fail at 1.