For your immediate needs, a tutorial from @gryff, Geometry Nodes and Blender 3.3 Export. Part 1 An Object and Instances using 3.3, shows how Blender Geo nodes can be exported.
As for Blender 4.x, they have seemed to modularize their fragment shaders & changed the UI for Principled material. This is a definite downgrade for exporters, however, who do not have the same shaders. There are duplicate places to assign the same thing, and would require many changes with the sole benefit of merely just running as before. Most blender improvements are not really exportable, anyway.
Exporters are not really Blender’s core focus. 2D renders & video creation is. We are just riding for free. Fortunately, every version of Blender ever published is available for download, Previous Versions — blender.org. If you have used it long enough, you will discover that their breaking of compatibility is going to nip your prior work.
The exporter is very mature, and only going to be maintained for bugs & things which are actually going to benefit BJS.
One bug, Proposal: Support `Alpha` settings in material even when image texture's file format is PNG · Issue #70 · BabylonJS/BlenderExporter · GitHub, is highly likely to be implemented. This change is needed to do for security reasons. The 2 stage loading I have implemented, goes thru a Container. This requires that textures be inline / embedded. Alpha needs to be controlled by other than the images file extension name.
Fortunately, this is both minor & I already have an example showing the problem.
The only thing being considered for improvement, is an input JSON file with changes to materials made in the browser to be mechanically updated in the Blend file. In my work, I am already writing things changed to materials in a .txt file using a web server with put capability.
The exporter can assign many things that Blender does not even understand like Iridescence & Parallax, & Environment Intensity. Once you start working with things like this, you no longer really care what it looks like in Blender, but how to get the changes back into the Blend file.
My in scene material editing, all that can be changed to suit the actual implementation look of things. I may also improve the editing by putting the UI needed on one of the arm panels I have, rather that a dedicated scene.
Sorry if this is not the answer you wanted. If there is no interest in change imports, then it will not be implemented for the JSON exporter.