Edge Profiles not displayed in Model Thumbnail

You were actually much closer in Version 6 - Although 10 Years ago, the Thumbnails were far sharper! I did say 'Appear to be back to normal’ in my previous post. However, upon closer examination the ‘Fix’ appears to be caught somewhere between the two extremes, and still has ‘Muddy Colours.’ For me, it is at least an ‘Improvement’ on the ‘Fat Profile Thumnails,’ but still falls into the ‘Could do Better’ category. Using SketchUP 2018 is only a ‘Work-Around’ and NOT a Solution! Why ‘Fix’ something, when it was not ‘Broken’ in the first place?

My suggestion would be to read SketchUp Desktop 2021.0 | SketchUp Help and specifically the model display.

Unfortunately, I cannot talk about the future . . . ?