I still own some Billies made in 1995 or so by Ikea. Literally massive wood and damn good book shelves. The ones bought by me in 2008 or so very noticeably less well build but still ok. The ones we bought in 2018 or so are shit, especially the shelves are so thin that they begin to sag.
In 2008 or so a friend of mine bought a "kallax" (another name then) and it was awesome, it's still in his basement and looks good. We bought one in 2023 and it's basically only paint, some "wood" and air. It's ok to store stuff in, but it's impossible to drill a screw into the wood. It's like trying to screw paper.