I think that, in terms of home decor, ultimately what “looks good”, is whatever has been thought about and actively chosen by the person that lives there - whatever suits them and their lifestyle and they enjoy
looking at and using as their living environment, has been carefully considered, carefully executed and cared for/maintained.
Homes are not photos on instagram or in an interiors magazine, they are a “living environment” as in both a location where people spend their time being humans and also an ever changing place that reflects what is going on in it at any one time (ie emphasis both on “living” and “environment”!).
Everything else is just either personal style, or following trends (which is not an inherently bad or good thing, but just is what it is). I loved what Sarah Beeny said about taste on her show recently, so I screenshot it
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Basics are clean enough to be hygienic and not look uncared for, and “tidy” whatever that means for us as an individual - we all have different levels of stuff that we can manage and keep under control, so however much stuff is in the house it needs to be within the occupants clutter threshold and kept on top of in some form. And maintained - items cared for and kept in working order, any damage repaired etc.