If you buy the lowest quality, it is composed of "particle board" (AKA pressed sawdust) and "corrugated cardboard" (https://youtu.be/24F5JlKkxR4?t=76). This furniture is incredibly easy to break and it will often not support being screwed together twice.
If you buy the higher quality furniture, which is often soft wood like pine (which is still incredibly low quality compared to traditional hard wood-based furniture), it will stand up a little better. It still scratches easily, because it is soft wood, but at least you can reassemble it after it has been disassembled.
Does Ikea sell any traditional hardwood furniture that is made out of things like maple, oak? I think not. Did they ever? I think they might have early one, but I could be wrong.
To be honest, it is likely a net environmental win that Ikea uses these cheap and low quality woods and sawdust and cardboard. Pine grows so much faster than hardwood, and reusing sawdust and cardboard is really low impact on the environment. I guess you have to balance that against the shorter lifespan of its furniture.