"but was the overall art culture so set against art as a craft to be perfected as it seems to be today in the past? I think about all the old masters who worked for years practicing and studying to be able to make great art, and compare that to today when the most celebrated “artists” are whoever can be the least talented and most offensive to the correct groups. Am I merely losing historical perspective here, or is the cultural of fine art these days demonstrably different (even if just in degree) than that in the past?"
OK... I've strugged pulling an answer to this together, and I'm not sure whether it's really an answer, or not.
As I noted earlier, each age has undoubtedly had its share of hack artists. But not all hack artists remain hack artists, and not all "great" artists who are lauded in their time remain great artists. It can take generations for an artist to be recognized as a great artist.
The fundamental underlying nature of the artistic process has also changed incredibly over the last several hundred years, and that has had a profound effect on both art, the artistic vision, and the number of working artists.
The most dramatic influence on art, ever, was the Industrial Revolution. It profoundly affected the entire structure of society and life, and that spilled over into art in ways that you really woudln't think about.
Prior to the industrial revolution, an artist was largely considered to be a craftsman, not unlike an architect (many artists were architects). In other words, it was their job, and as with any other job, you needed to be paid, or you didn't eat. That meant you needed a wealthy patron, or more than one.
The biggest and most influential patron of the arts was the Catholic Church. After that came the kings and major royals, and the leading trade magnets like the Medici family.
Given the Church's influence on just about all aspects of life, it also set the tone for much of the art. Artists didn't have the ability to experiment. If they did, and got too wacky, the patron (especially the church) generally didn't like that much, so realism ruled.
An interesting exception to the general realism rule was Hieronymus Bosch, but even his fantastical artwork was couched in deeply religious themes and was highly allegorical and meant to convey religious themes to the viewer.
The industrial revolution changed all that.
First and foremost, it helped break the stranglehold the Church had on art by starting to break the stranglehold the Church had on everyday life. When that happened, the church also started to lose control over the way artists depicted the world. The Impressionistic movement simply wouldn't have been possible in the 15th or 16th centuries because the Church would have slammed the door on it.
Associated with that was the industrial revolution made a lot of people very wealthy very fast, so it dramatically broadened the number of patrons available. More and more marginal artists were able to make a living at it. Even more people, who didn't become wealthy, became well off enough that they could participate in the art world.
The industrial revolution also dramatically reduced the price of the tools of the artist. New, cheap synthetic pigments replaced expensive natural pigments such as crushed ores and semi-precious stones. Paper plumeted in price as the fourdrinier process took hold, and cheap canvas, woven on steam looms, replaced wooden panels.
Finally, industrial revolution gave more and more people something that they had never had before -- leisure time. Even the lowest working classes began to get time off because they either earned a living working in a factory, or the industrial revolution's advances in farming allowed them to produce more in less time, reducing the amount they needed to work.
And when you've got leisure time, some people's thoughts turn naturally to art, so you had the rise of an entire new class of artists -- the part-timers.
So, I guess in large part, you can blame modern art on the industrial revolution.
