With my knowledge as a non-professional woodworker, there's not a lot to cabinets. Even professionally made cabinets use veneered plywood for the bases so what IKEA does isn't any different than almost all cabinets here in the US. The US mostly uses 'framed' cabinets instead of European 'frameless' cabinets, but the cabinet box is essentially the same.

wood expansion is a big factor for wide flat pieces. Non directional wood products like MDF are used in cabinetry because they do not expand to anywhere near the same degree as solid wood. If you want to use solid wood you have to float it in panels, like you sometimes see on doors. But that adds a lot of complexity. For cabinets where you have dozens of moving pieces using MDF (or plywood) is much better for the reliability of the moving parts.