This is the answer IMO. Godot is lightweight, easy to use, and free with fully open sourced communities. Check out GDQuest for tutorials. The best part is that Godot uses a programming language called GDscript which is based on Python. I've learned so much about programming best practices using Godot that it translates to my day job now when I need to use python. I cannot recommend it enough as a hobbyist.
As an additional point, Godot 4 just released and it is really giving Unity a run for it's money with features and capabilities.
For a reveal stream they really didn't reveal much of anything. Let's hope we get more info about the season mechanic like PoE does leading up to launch. Excited to get back into diablo!