If you want solid wood desks and furniture, then ikea is terrible quality. If you want a desk that a 10 year old can pick up and move on his own, ikea is great quality.
Ikea has solid wood furniture. Their sofas, at least the one I bought, the frame was solid wood. The table and benches I bought from them was solid wood. Some dinning room table and chairs I bought from them were solid wood. The kitchen island cart I bought from them was solid wood.
The famous KALLAX shelves and MALM drawers are not solid wood but just because some of the their furniture is not doesn't mean all of it isn't
Their wood products are made from some composite wood chips, MDF, with glue, or something (I’m sure someone will reply with the correct product names). Not only does it exude VOCs for months or years to come (again like McDonald’s, affecting your health unless you use indoor air filters), but the wood products often crack off at the edges.
Their plastic products are made some quality of plastic that is too thin. They don’t break in my experience, but I question Why they are so thin to begin with.
The thinner it is, presumably the easier it is to pack and load.
Flat-pack is all about efficiently making it easy to carry in the car, and also trying to shove as many pallets into a truck or warehouse as possible. In a similar vein, much of what used to be glass or metal is now plastic, because it's lighter and thinner and you can use the space saved to pack more into a pallet.
The famous KALLAX shelves and MALM drawers are not solid wood but just because some of the their furniture is not doesn't mean all of it isn't