Check out the new stable and current build of Godot with quite a few changes from the last stable version (3.5). Almost everything in the engine has been improved including: 3D rendering, level editing, visual effects, shader editing, scripting (both GDScript and C#), physics, XR/VR, networking, audio, and animation. Check the link for more details.
And while these features are quite a step up for many developers, more importantly the core of the engine's code has been improved which may not be obvious to users of the engine apart from performance improvements. What this means is future development on the engine has been made better to maintain and expand than before. This is the key that makes Godot 4 such an important update for the future of the engine.
I am personally very excited to see a free and open source project reach such a goal. This is an impressive engine for such a small package and will enable a lot of creative people to realize their game and software creating dreams.
You can also watch the full breakdown of the engine's features by GDQuest here: