I think there are 2 questions here that are important to untangle. One question is "is it art?" and the other question is "If it is art, who is the artist?"
It's my stance that the second question is the more important one. AI is already capable of producing things people find beautiful, sometimes meaningful, and occassionally even passes as human-made art. So, if it's capable of being experienced as art, there's in my mind not much of a difference between being indistinguishable from art and being art. So, just for a second, let's take it for granted that AI art IS (or can occassionally be) art.
Once we take that for granted, we can still ask "So who is the artist?" Some people liken AI to a tool, and when they say that, they're implicitly (sometimes explicitly) making the claim that The Prompt Writer is the artist. I think that claim is very, very contentious, and should be questioned.
In a pre-AI world, in the world we lived in just a few years ago, before Midjourney started turning heads, people still made prompts for other intelligences to interpret and make art out of. Those other intelligences, taking the prompts and making art, were other human beings. We call this a "commission". When you give a prompt to another human being and they make a picture for you, most people DO NOT consider the Prompt Writer to also be The Artist - they consider the person who actually produced the imagery The Artist.
If I paid an Artist to depict a prompt, and then later presented the finished piece as my creative work, and called myself The Artist, people would generally consider that dishonest. That's basically plagiarism or creative theft.
I believe AI art should, in 99% of cases, be considered analogous to this. Instead of paying a person and giving them a prompt, you're now giving the prompt to an AI -- but it's still effectively the same as the Commission scenario. You're giving a prompt to someone (or something) else - some other intelligence - and they are taking your prompt and turning it into an image. If you shouldn't be considered the artist when another Human makes the image, why should you be considered the artist when an artificial intelligence does so? In my opinion, you should not.
Now, I would like to carve out a little exception here for some people who use AI art as part of an artistic work flow, and don't just take what the AI produces and calls that their finished work. There are ways to use the output of the AI fairly - but most AI images are not using the output to produce their own art, the output of the AI is in 99% of cases the finished piece, and in those cases, it's essentially a commission.
So if the prompt maker in 99% of cases isn't rightfully The Artist, then who is? Perhaps the AI itself? Perhaps the programmers and designers of the AI software? Perhaps the thousands and thousands of artists whose work was used to train the AI? Perhaps all of the above have a stake. I'm not sure about the answer to that.
AI is not "just a tool" in these 99% of cases. No tool previously made so many creative decisions as AI does. AI is a commission artist, not just a tool, in most cases.