Aren't healthy INTPs supposed to be really open minded though?
And how about ENTPs do they suffer from the same problem?
Yes. Key word healthy ones. When in touch with their Ne, INTPs can be plenty open-minded. It's when they get stuck in a TiSi loop that that they can become closed-minded. Similiar to how ISTPs and INFJs can get in a NiTi loop where they see infinite perspectives and can't decide on any of them.