The overuse of linked lists as a 'Data-structure'. This means the engine misses out on a lot of possible optimizations.
There was an issue about this. I encourage you to read the whole discussion to see why those design decisions were made. In general, Godot aims for ease of use rather than absolute performance.
The OpenGL renderer does not use 'culling' or 'batching'. The result is the engine draws everything on individual draw calls. This MASSIVELY reduces the frame rate (FPS).
2D batching was implemented in 3.2.2. It's enabled automtaically if you use the GLES2 renderer. It may be added to the GLES3 renderer in 3.2.3.
In 3D, you can use MultiMeshInstance to merge 3D meshes together into a single draw call. If you need to do lots of processing on thousands of instances, you can also interact directly with Godot's servers.
The inability to load assets from a 'stream'. Only files, so a 'game archive-system' is impossible for this engine.
What do you mean? PCK is precisely a "game archive" format as it's basically a virtual file system.
As for texture streaming, this is coming to Godot 4.0.
There seems to be a large disparity between the praise that the GoDot engine is given and people's actual experience with it. I'm not here to argue with you, merely to bring to light the issues that prevent GoDot from becoming a world standard. From what I've been hearing, these problems are so bad that people have suggested that GoDot or a large part of it should just be re-written.
Godot is a do-ocracy. If you want your voice to be heard, you need to contribute :)
We've had "experienced programmers" tell us what to do for years now, but I would really appreciate if they could make more meaningful contributions. Even contributing documentation or demos goes a long way.
With that said, I think its important to also mention its strengths. From what I understand, the engine itself is free. The costs of developing it are paid for by the online market that sells code and other assets.
There's no official marketplace, actually. The engine development is funded by Patreon (which I'm not part of) and various sponsors.