It's simply not true that the main advances in generative art were made in the 50s and 60s and nothing new is being done now. Generative art is a huge, thriving field right now with thousands of communities and subcultures around it, using traditional coding techniques or visual programming systems like TouchDesigner. Honestly, just reading through this thread for yourself should be some perspective on this.
That's not even counting new tools like DALL-E or Midjourney, though personally I don't think we can write them off as uninteresting or low-effort. They're an exciting and powerful new tool, and like any tool they can be used to make art. Maybe as an artist making art that others could not also easily make is important to you, but that is not what makes art.
As an activity art implements ideas that have been formulated conceptually previously ("conceptual" here could be a drunk artist taking a pic of their butt and isn't philosophical + more related to surprisal). The immediately exciting thing about art is the experience of the product but that experience gives way to a more conceptual excitement (its interesting because they are exploring this idea!). When an idea is repeated x amount of times as an artistic expression it gets boring. Generative art is boring on these terms, to me, right now, even if many technical advancements relating to the speed or complexity of the generative system are made.
H/w this is just a fun argument about art which is basically impossible to concretely describe anyway and i'm prob wrong (e.g. some kid is going to make something incredible with a new idea about generative art x AI).
I see what you're saying, and defining what makes art is nebulous to the point of being impossible. Rather than a positive proof, I would just counter by asking whether you think art can be defined purely by its aesthetics, or by virtue of the methods used to make it - that is, without considering at all any concepts or ideas put forward by it.
It's got to be a combination of both (e.g. made from wood and shaped like a ball but feels like this in this room etc) but maybe that is too neurotic and not conducive to new aesthetic experience. I think my pattern recognition for generative art would be quite high based on how many times I've seen it as a style of art previously. For most images i've seen DALL-E has all of the fingerprints of generative art and on some level I notice that even if the fidelity is approaching something that takes over aesthetically (e.g. where those kinds of perceptual fingerprints fade away a little bit).
That's not even counting new tools like DALL-E or Midjourney, though personally I don't think we can write them off as uninteresting or low-effort. They're an exciting and powerful new tool, and like any tool they can be used to make art. Maybe as an artist making art that others could not also easily make is important to you, but that is not what makes art.