"plasticized" sounds like something is going heavy-handed on the noise-reduction.
What happens if you shoot the images as 'RAW' and don't process them (all RAW images need a bit of adjustment ... but just for the sake of testing, if you were to do this would your images still look 'plasticized'?)
" My Canon 6D Mark II, leaves a few smooth * plasticized * photos, should be in the image / sharpness / sharpness / clarity / limit style"
Reset the camera back to factory default. In Tools tab clear all settings. You set something up wrong and now you need to go back to square one. Don't try to fix what you have until you know what you have.
Your posting of this photo, together with your previous comments, suggests that you don't understand "depth of field". Google the term and read the resulting articles, giving particular attention to the effects of aperture, focal length, and sensor size (e.g., the difference in behavior of full-frame and APS-C cameras).
To Bob's point... did you intend for this to have the blurred background? Is that the "softness" to which you were referring?
The focused subject's face does look sharp (at least it does at this size).
Your depth of field is shallow (subject's ears are less focused then their face... their shoulders are much less focused.) Depth of field is primarily properties of a combination of focal length, focal ratio, & focused distance (i.e. your lens choice & setting choices.)
In an indirect way, sensor size also influences depth of field. It isn't the sensor size per se... it's that SINCE the sensor is larger, a photographer is likely to stand closer to the subject (assuming same focal length lens) to capture a similar composition (vs. where they would need to stand if they had an APS-C crop-sensor size camera and wanted that same composition). It's that behavior change... the fact that photographer chose to stand closer... that creates a shallower depth of field.
Regardless of the reason, it is generally accepted as something that portrait photographers prefer ... a shallow depth of field that renders the subject sharp, but a background which will pleasantly blurred.