A similar thing happened in the early days of 3D printing. When hobbyist 3D printing started you needed to be skilled and tenacious enough to build a 3D printer and tune it well enough to print.
Then as companies like Prusa and later Bambu made 3D printing more and more accessible to the masses there was a subgroup of 3D printing fans who were unhappy about the change. They lost interest in the hobby. Some became bitter and spent their time finding things to complain about on Reddit and other forums instead of enjoying their printing.
Logically, enabling other people to produce something shouldn’t subtract from others’ enjoyment of their own hobbies. Many still do woodworking with hand tools even though we can buy factory furniture now.
I think some people are more interested in seeking status and doing things for personal branding reasons than the joy of the hobby itself. For that group, any advancement that makes it easier for other people to do something similar to what they do (even if lesser quality, as is often the case with AI) it interferes with their ability to use that hobby for status. They carved out a niche as the person who did something rare or semi-unique, but making that thing accessible to more people took that away. So their motivation wanes.
It's also interesting to note that there's a distinct delineation in "before Bambu" and "post-Bambu" in communities with a DIY part to them - there's been a humongous explosion in creativity and functional, valuable output ever since the cost of entry went from "you gotta own a metal shop or a wood shop" to "buy this one $1000 machine and a hardware kit".
For example, I remember frequenting the NerfHaven forums back in the day, and people were designing Nerf blasters in Solidworks, printing drawings out, gluing them to polycarbonate, and using scroll saws to build their own blasters capable of 150fps. Nowadays, I can buy a printer, a hardware kit, and build my own 200fps capable blaster in an afternoon, and there's probably 5-10 new interesting, fleshed out concepts a month.
The explosion in depth, detail, and accessibility in DIY cosplay designs is also incredible.
When the hobby devolves to "load this file and click 'print'" then the people whose reward was found in the actual creation of the thing get disillusioned. Not sure why, because they can still do things the hard way, but I guess it seems pointless.