Parmandur
Book-Friend, he/him
Not watered down, but rather focused: Ravnica was focused on providing weird urban fantasy genre material, Eberron was focused on providing pulp adventure material in a post-WWI like environment, Theros was focused on Hellenic Myth genre material, Ravenloft was focused on Gothic Horror genre material, and Strixhaven was hyperfocused on magical school genre material.Whether they are separate books or combined I imagine they will be watered down. That is "The Way," for 5e. I just think you could get some interesting cross pollination with one book that you are unlikely with two.
Spelljammer and Planescape represent completely different genres: space opera and weird fiction. I am down to mix them in general terms, but they belong in different books to allow for genre focus.