Is it very weird of me to find extremely odd the combination of

• confident pronouncements about whether a piece of music written in 1845 could have been written in the 1820s
• confident pronouncements about the processes by which music made its way into the canon in the 1800s
• apparently being completely unfamiliar with Robert Schumann until the last few days?

I mean, it's not as if Schumann is obscure or third-rate; he was, as you say, enormously influential in shaping critical opinion and he was a composer of the first rank (yes, especially for piano, but it's not like no one plays his symphonies any more). Doesn't being "not familiar with Schumann" strike you as a disqualification for telling us what the "main criterion for artistic greatness" was (in the context of music) in the mid-to-late 19th century? I mean, what business have you saying such things when you're "not familiar" with someone who was both central in deciding "artistic greatness" then, and one of the leading exemplars of "artistic greatness" then?

I'm aware that this sounds rude, and I'm sorry about that. But there does seem to be something of a disconnect between your willingness to complain of how little artistic success for 19th-century musicians had to do with quality, and there being at least one really big hole in your knowledge of that period.