Have you looked at Godot 3 at all? What missing tools and editors? In reality, it's missing as much as Unity or Unreal in that you still need to create your assets somewhere else, such as in a 2D paint program, like Photoshop, or a 3D modeling app, like 3DS Max. But you have the editor where you can add your graphical content, be it for 2D or 3D, and a full coding environment, including the ability for visual coding (mainly for non-programmers). Godot does not appear to be "lightweight" at all, actually.
Have you looked at the feature list? Read about it here:
https://godotengine.org/article/godot-3-0-releasedWhen it comes to 3D, it features things found in AAA engines, such as:
PBR Rendering:
FULL PRINCIPLED BSDF:
Global Illumination:
Mid and Post Processing:
GPU Particles:
GLTF 2.0 SUPPORT:
[img]
https://godotengine.org/storage/app/media/3.0%20release/gltf.png[/img]
And so much more!
And, best of all, it's open source and free, including exporting to just about anything:
Mobile platforms: iOS, Android
Desktop platforms: Windows, macOS, Linux, UWP, *BSD, Haiku
Export to the web using HTML and Web Assembly
One-click deploy & export to most platforms. Easy to create custom builds too.
I would highly recommend you check it out.
