As you see, everything is a matter of good meshes (e.g. realistic cloth wrinkles), good high res textures, good shaders (e.g. curtains), good composition (e.g. viewed in front, from human eye level) good lighting and subtle post production. If one of it is not good, it will break the whole image. Sticking to real world photography imagery and principles is a key for realism.
Also what is important, that people forget that sometimes realistic results are not always possible to achieve because of the ugly designed furniture, used weird colors, bad interior design. Sometimes people wants something that is so bad that is not eyecatching and it breaks realism - because we’re not used to look at unusual design; good example is an alien design in movies, even if it has extraordinary shading, lighting etc. but it’s not based on widely known humanoid design, it can be received as not realistic or not convincing.
I am interested in this topic, I should say I agree to what you mentioned. Based on my experience Cycles responds well when there are a lot of objects in the scene meaning a lot of light interactions, otherwise it will look dull & soulless… Corona is still the king but its new tone-mapping is really annoying & distracting IMO.
It has become my paradox too that I work fast in blender because of its tools but when it comes to render I am exhausted from the very beginning…
