simple-minded
adjective disapproving uk/ˌsɪm.pəlˈmaɪn.dɪd/ us/ˌsɪm.pəlˈmaɪn.dɪd/
头脑简单的，愚蠢的
A simple-minded person does not have the ability to use reason and understand.
（行动或态度）幼稚的，想当然的
A simple-minded action or opinion is based on a limited understanding of a situation.