My main concern is how this will affect new players. You’re losing the opportunity to teach them what needs to be entered, as well as the opportunity to teach them implicitly about what “the battlefield” is, and zones of play in general. The more knowledge that you need to already have before you can understand what a card does, the less accessible the game becomes. And this is while they’re trying harder than ever (via Universes Beyond) to attract outsiders.

I see why they did it, but personally I think saying “When [creature] enters, …” sounds weird. It wants a noun after it when I hear it. It sounds like “enters the room” or “enters stage left” when I read it. It also kinda makes ETB no longer mean anything, and I really like that abbreviation 😕