This sounds like what is called the soap opera effect:

https://en.wikipedia.org/wiki/Soap_opera_effect

Which is generally associated with excess denoisong rather than with excess grain.

Are you sure? That seems to be about motion interpolation. Not even about smooth motion, but about it being interpolated. Here the concern seems to be about how the individual, still images look, not anything about the motion between them.

> some series and movies look too realistic, what in turn gives me a amateur film feeling

This comment that I replied to is almost a textbook description of the soap opera effect.

The interpolation adds more FPS, which is traditionally a marker of film vs TV production.

Avatar 2 was particularly egregious with the poor interpolation

i think i've seen this effect on tv shot on cameras that were lower fps than the tv outputs. looks fake and bad and interpolated because it is.