oversimplification

US /ˌoʊ.vɚˌsɪm.plə.fəˈkeɪ.ʃən/
UK /ˌoʊ.vɚˌsɪm.plə.fəˈkeɪ.ʃən/
1.

the action of describing or explaining something in such a simple way that it is no longer correct or true:

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The book was full of oversimplifications.