Newbies showing off their first triangle are welcome over in r/gameenginedevs/ and r/GraphicsProgramming/ :)
But I think it's a combination of "people have short memories" and "people don't like change"
https://gamedev.net/forums/ is the classic hang-out spot.
That 'first triangle on screen' code can now look something like this - https://github.com/KhronosGroup/Vulkan-Samples/blob/main/sam... - compared to the simpler old days of OpenGL (https://github.com/gamedev-net/nehe-opengl/blob/master/vc/Le...)
But fast, general purpose rendering engines are hard. Not impossible, just hard. In open source land, we have about a half dozen examples of My First Rendering Engine, and they mostly work. But they don't scale.