Honestly, it would be exhausting to list all of the problems with ERP that I have learned over the many years I was doing it. There are just so many that you come across, people with bad grammer/spelling, people who fail to differentiate between actions and spoken word, people who insist on you RPing as something, or in a way, that they specifically want, people who can barely manage 1 sentence at a time, people who write entire essays at a time, people who insist on their fetishes being catered to but they won't do the same for you, the list goes on and on.
I eventually just gave up on ERP all together, its too much of a headache and its too rare to find an RP that is actually good and can last. I've just resorted to AI for my ERP needs, sure its not great, but at least I can have some amount of control over how bad it is.