I think it depends on the rhythm of your story and, for me, that is an important aspect.
That being said, there is a wide variety of chapter lengths. For a MG, I agree that I wouldn't go far over 1800ish. My personal preference is short chapters. It keeps the story moving and the young reader engaged.
With regards to word count, I do know the trend is for longer stories, but my debut coming out next year is 20250 words, so there are always exceptions. I think if the story is very good and the voice is there, but they think it's too short, they'll ask you to revise.
Ree