Hi Murat,
Your description helpfully narrows it down, although it remains to be seen if an explanation can be found
Often, one thing affecting perception of "richness" is the level and type of reverb (often system reverb set within the style). Preset voices when selected bring in their default levels which usually are quite low for my taste, resulting in a relatively clipped if not dead sound. That's why I asked about your testing, if you test presets you may (anally hehe!) interpret these as inferior in their unedited state compared to what you expected from pre-update playing sessions.
Similarly there is quite a difference in perception of richness depending on whether the system type has been set (in the extreme) to the old Hall1 or one of the later ones such as MediumHallPlus or LargeHallPlus.
I can't explain why updating could have altered such settings, and am still not convinced it has. But if you are looking for optimal richness, it may be useful for you experiment with reverb and come to some conclusions.
If you remain convinced the update was the trigger there is always the option to revert to the previous OS and check again. (You later have the option to download a fresh copy of 1. 41 and re-update on the basis that so far no one else has reported a quality issue.)
John