I think there is still some progress in the arts.
We find more recent works more interesting than older ones, not necessarily because they're better, but because they speak to us more usefully -- similarly, we can find surprisingly old works surprisingly relevant for the same reason, or can rediscover materials that previous generations scoffed at.
Most of the plays of Shakespeare fall into this last category -- they were hardly ever performed in the late 17th and 18th centuries, and when they were, they were jazzed up with special effects along the lines of fireworks and performing bears. The gulf between the 18thC and our own is an enormous one in general, come to think of it; play _Empire: Total War_ for a sense of just how different even the visual aesthetics of their era were from our own.
Don't look at the art assets that are, necessarily, more or less faithful to the period; look at how the game's developers try to make the era look interesting to a modern. What most stood out to me was the vast gulf between the national flags used in the 18thC and national flags depicted in the game -- in particular Austria, where the red-and-white national flag is replaced by the yellow-and-black dynastic flag of the Habsburgs, and Russia, where the white-red-blue national flag is shame-facedly tacked on to the Romanov coat of arms. (The loading screens are the second most extreme illustration.)
Joyce is not better than Shakespeare and Prince is not better than Mozart.
This is even truer for painting, would anybody say that we are doing better than the Altamira cave painters?
I will say this; I have a clear preference for some modern stuff over the older stuff. The biggest one is modern TV vs. older TV; going back to 1960 or 1970 and trying to watch TV for me is simply infuriating; it's all so damned slow. Actually running it 30% faster (as in, watching it literally sped up 30%) helps quite a bit.
My point is that, in my opinion, there is no progress in art exactly for the reason you have just given that there is no objective "better" to measure progress with.
About TV..., if you are talking about TV shows I wouldn't consider them art at all.
Ernie Kovacs.
Also Playhouse 90.
Also tautological depending on your definition of "art". The definition I favor doesn't disqualify something for the medium it is in, but it certainly isn't the only relevant definition.
To point it out is pleonastic.
The following sentence is tautological.
The previous sentence is tautological and pleonastic.
"TV isn't art" carries a lot of connotation, but no actual denotation. I object to just lobbing the connotation into a conversation and acting as if something has actually been established.