Retaining a bezier (rather than converting the bezier to vertices) would help reduce the PDF size, as you have said.
What I have noticed, though, is that a lot of publicly available data (EX: GIS data from municipalities) seems to have been created without bezier curves to begin with. The data has a large number of vertices at point of origin. I'm not sure it's feasible to have software generate bezier data where it didn't exist before.
We have been getting around the large file sizes by doing two things:
1. Testing out the use of stylized vector base maps that are already optimized. There are some layers that I turn off labeling on the base map and bring in my own because I can refine the label placement better (EX: Highway Shields / road labels).
2. Exporting the PDF from ArcGIS Pro, then opening the file in Acrobat Pro. From there I go to File / Save As Other / Reduced File Size PDF. This seemed to handle vector data better than "Optimize". It is still not as small as your AutoCAD example, but it was still a vast improvement.
You can also experiment with your layout size in ArcGIS Pro. If your Pro layout is 24x36 you'll need to work a lot harder to get to a reasonable file size. I find that an 11x17 layout, exported at high quality, is more than enough to make plotter sized enlargements from--especially if most of the data is vector. Using this layout size, combined with using Acrobat to reduce the file size, has reigned this in enough to have a fairly usable workflow while waiting for another solution.
Regarding rasterizing, Pro already does this reasonably well and it is fairly easy to get a good raster image if you start with a good quality vector. While the Output as Image option added will at least help those without other graphics software to do this task, I hope that ESRI's development focus will continue to be on VECTOR optimization / generalization at export.