I have an extensive playlist of the works of many lesser-known composers mostly of the 19th century and most of my CM listening these days is of their works. Given your fixation on the 2 or 3 composers (particularly M.Haydn), you keep mentioning, I just may have more experience with lesser-known composers than you.People who don't listen to those lesser-known composers and still make judgments about them — Are they really different from 99.99% of people in the world who think classical music is simply too outdated to be taken seriously? We are just closed in our nerdy little circles. It's questionable for whom this "objective greatness" thing is relevant.
Composers of the period 1000~1700, it could be said that their music is simply less accessible than Bach, Mozart, Beethoven.