I too only discovered in the past month that the 3D model contributions of SketchUp enthusiasts ceased to be accepted last October.
Like many contributors, I don't do this all year round, and had taken a break from this most satisfying of pastimes. I often refer to it as "the best game on my PC".
Resuming my hobby in March this year, I lovingly created a new model and went to upload it to the 3D Warehouse, only to find that everything has gone. No more community comments and ratings. No more upload to the Google Earth 3D layer.
I haven't been as prolific in my geo-modelling as some, but I return to the hobby when the creative and contemplative mood takes me. My contributions are at
https://3dwarehouse.sketchup.com/user.html?id=1560172616518437420763610...and I have a couple of other models that I have not finished, one of which has been on the go since 2011! I was in no hurry. Now it's all wasted.
Truly saddened by this. Many, many people I am certain will feel exactly as I do. And there will still, even today, be those who are unaware of the cancellation of the GE 3D Layer pipeline.
--Thomas (aka 3dBloke)