It's not just having to use simple words, but also simple concepts, simple topics, etc. The real problem is that talking this way is exhausting. As if someone

It's not just having to use simple words, but also simple concepts, simple topics, etc. The real problem is that talking this way is exhausting. As if someone told you that e.g. you are not allowed to use words containing the letter "m". It is certainly possible, but it requires constant attention to something other than the idea you are trying to convey. Talking this way feels quite different from talking to someone who uses the same style as you.