In this forum, there is a lot of conversation about the rendering of lenses and lenses with personality. The sharpest and most corrected isn't always the best, in contrast to what the photo mags would usually have us believe.
I have a Yashica D with the 3-element Yashikor lens, which is very similar to your former 635. I also have a Yashica-Mat EM. The Yashica D is a different animal from the 'Mat. It doesn't have the lever wind, which is the Achilles Heel of the 'Mat. Instead, it has a simpler, more robust knob-wind and manual shutter-cocking. I bought the D because I wanted a simpler lens for portraiture, figuring that a little added softness and vignetting would be a good thing in this application. Also, having a bit of a purist streak, I figured that the simpler the lens formulation that would do the job, the "purer" the image. 😉
We have members here in love with their old folders, early Rolleicords, and such, with their Novar, Triotar, and similar lenses, for their rendering personalities. Nothing mad about that. I think you are in good company and I would recommend you find yourself another Yashica 635 or Yashica D. At least the camera you miss is one of the less expensive to replace.
- Murray