* The POÄNG chair is a copy of Alvar Aalto's 406.
* Nakamura's earlier POEM copied both the 406 and a chair by Bruno Mathsson.
* FROSTA (now discontinued) is a copy of Aalto's Stool 60.
* KROMVIK copied Bruno Mathsson's Ulla bed frame.
* BORE copied Mathsson's Karin chair.
And so on. Ironically, some of these also have become classics of their own, or at least sought-after vintage objects.
IKEA sometimes comes up with original, sometimes novel designs, but generally they copy better designs with worse manufacturing quality rather than coming up with original ones.
And they are genuinely worse in terms of construction. For example, if you compare the wood quality of a FROSTA with Aalta's stool it's night and day. FROSTA is just plywood cut to size. The Aalto stool is solid birch, with a plywood top and an elegant solid birch veneer for the edge band, and the legs use a unique plywood-like join that is a thing of beauty [1].
[1] https://www.alvaraalto.fi/wp-content/uploads/2017/10/l-jalka...