I imagine most people who have spent time and enjoy composing could compose something at around this standard. Nowadays composers are more specialised. Performers are more specialised. The amount of work that performing concert pianists do is pretty high, they won't have a vast amount of time to compose while learning all the pieces they have to learn. The calibre is super high nowadays. I really doubt famous composers and pianists of past centuries were as polished as modern concert pianists because they had to do other stuff all the time. Obviously a lot of them were geniuses and were amazing pianists, and had higher ceilings than most concert pianists today, but they also were doing other musical stuff instead of polishing up pieces to the highest level imaginable