Actually, teachers are human beings and they're allowed to have preferences, likes and dislikes. It's okay that not every teacher is for every student 100% of the time. Something can be a bad student/teacher fit without it being a negative value judgment ("sad", "gatekeeping", "drop").
teachers are held to a higher standard because their responsibility is a lot higher than the average citizen, so while theyre fully allowed to do whatever they want and have preferences -- i won't hold them to a standard that i do an average person. they need to above all have the highest patience and the least amount of gatekeeping, full stop.