a big part of being experienced in this hobby is understanding room interactions and how gear setup (most importantly the listening triangle and proximate room boundaries) affects how the sound is heard by the listener
with a good understanding of this, once seeing a room and the system set up within it (or some good pictures of it), one has a decent idea of how the rig will likely sound... not 100%, but i would say at the 60-70% level, assessed by experienced hands... of course, some difficult rooms can sound quite good if the owner knows how to configure the system within it, manage the deficiencies ...
all this said, this doesn’t make any reviewer’s work worthless... as in all situations where advice is being sought and given, the recipient is wise to understand where the advisor is coming from, the operating context and experiences that may shape the views and assessments given... a cancer surgeon will often advise resection as the best course of action, whereas the leading oncologist may lean towards chemotherapies... it's just human nature, predictive of how human experience is gained over time and how views are shaped
