IMO they still aren't big enough, and I own a 2018 S. I have to hold my hand up to block the sun in early evening, which I've never had to do in previous cars. What's the point of sun visors if I still have to raise the seat or hold my hand up?
On some models, Lexus has sun-visors that are on telescopic arms so that they can be extended to cover the 'back' portion of the side windows (this would be really good for me as this is pretty much the only place I have a problem with the sun and normally means I have to drive with one hand blocking the sun so I can see). I also seam to remember one of my dads old cars (either a Lexus or Audi) that had this as well as a second thin plastic visor that could fold down to cover the front windshield as well.
This is definitely something Tesla should implement.
At first, I thought this feature was desirable, but as it turns out, I've found that for my height, etc. the current size is just fine. Therefore, I'd say leave the visors alone--except for adding lighting.