This is the raw data and it shows disproportional attention to the 18th and 19th centuries. I guess some will interpret it any way you like to support your argument.
But your second point, is exactly what I am saying. People concentrate on the earlier music in part because it's easier... they prefer not to challenge themselves too far beyond their comfort level.
I'll agree with you there. I went to a conservatory thinking I'm gonna practice only on my instrument but I ended up taking dozens of extra courses, and I am now making a living in music doing a lot more than just playing the violin-- teaching, writing about music, performing, composing, arranging...