That reminds me (in a rather postmodern way, I suspect) of an interview I recently read with a celebrity whose claim to fame is basically nudity:
Anyone can show their boobs. But they don't.
And your statement "Anyone can technically paint like Matisse. But they didn't." That's probably because noone wants to paint like a child and wants to be considered a good artist not a joke.
Believe me, in 1000 years no one will care about Modernist artwork.
Like other wealthy men, you too dabble in collecting some art. You own a few romantic pieces with exceptional craftsmanship. You proudly display them in your living room amid all your fancy, ornate furniture.
But something is amiss. All your artwork starts looking the same. And why wouldn't it - all these artists have honed their craft at similar art schools. They look good but they've started looking a little repetitive. Like something out of a factory.
You have to see artists like Matisse in this context. Try placing yourself in the shoes of someone from their period. Realistic art was dead because there can't truly be any further innovation in it (and the camera would make it obsolete anyway). The themes, the styles, even the figures had been all tried and put on canvas over the last several centuries.
A Matisse in this context is very new, very exciting, and very full of life. It's bright blue in dimly lit 19th century homes. It's a yellow dancing figure in a room that has only see scenes from the Bible and Greek myths painted.
This is the reason why its art.
"Looking pretty" is just craftsmanship. If it makes you feel something - even acute hatred - its art.
This is what I'm trying to state. Art is craftmanship then to you, since you can't understand that art requires skill or talent.
Additionally, the fact that you're judging the relative worth of a piece of art based on it lasting for 1000 years is pretty sad, in my opinion. What is wrong with art being created for a specific time and place? Life is ephemeral, and there is beauty in that.
Modern art is not art in the sense it's not a highly crafted work. It's minimum effort.
The time frame was given to acknowledge the fact that we think this is "art". In the future we will know this is junk and not art.
I really dislike most pop art, but at least it's art. A big yellow square canvas in no way should constitute artwork.
There are literally factories in China where painters paint replicas of classic art works at scale. They paint hundreds, even thousands of such pieces every year.
They're undoubtedly very skilled painters. But would you call their work "art"?
How much time and effort something takes has no bearing on whether or not it is art. Something that takes 5 years to make isn't automatically better than something done in 5 minutes.
Painters like Picasso and Matisse were also classically trained and had all the skills to paint like the painters of old. They just chose not to.
I was at the Hermitage museum in St Petersburg. I'd done museum tour after museum tour in both Moscow and Petersburg. Nearly all of this art was classical/neo-classical or romantic, rococo, etc.
By the end of your 1000th neo-classical painting, you get exhausted of the sameness of the realistic style. The themes, colors, sensibilities all appear similar.
Then I walked into the modern and post-modern hall and there was a massive Matisse painting on the wall. The bright blue was such a revelation. You see a painting like that after 400 years worth of realistic painting style and it takes your breath away. It was particularly impactful when contrasted against the neoclassical architecture of the museum itself.
The worst way to appreciate modern and post modern art is on a computer screen. These things have to be experienced in person. For one, their sheer size can't be captured on screen. A 12' x 10' canvas has a visual impact that's not possible to replicate anywhere. Second, their experimental quality has to be contrasted against the dominant art forms of their time. Anyone can technically paint like Matisse. But they didn't.