I know many here on FT don't like TripAdvisor, but I use it often and almost on every trip we take--almost all of which would be considered luxe. (We most enjoy casual luxury, so we love Aman, certain Peninsulas, certain MO, St. Regis, FS, RC, PH, and other luxe boutique properties, with a leaning toward smaller, more intimate type luxe properties when available.)
TA can be very helpful, but you need to parse the reviews and not worry about overall rankings.
I usually select for only 4 and 5 star properties to start. I then consider those properties and their reviews. I also try to focus on recent reviews AND reviews that are for the timeframe in which we'd be visiting the property--so we get a better sense of occupancy levels, weather, etc. for the time we plan to visit.
I then read the reviews from contributors who have a MINIMUM OF 25 REVIEWS. I disregard almost all others, and I NEVER trust positive or negative reviews from those who have contributed only a few reviews, especially since they so often talk about how often they stay at comparable properties and yet have not contributed any other reviews--making them dubious IMO.
I also look at the reviews on OTHER properties for those contributors whose reviews have the most priority for us on the property in question. If they have often reviewed comparably luxe properties or other places that I also have considered (all around the world), I feel their reviews have more substance for what we are considering. If they talk about how luxurious a property is and then seem to only have stayed at midscale or slightly upscale properties, I usually disregard their reviews entirely--as they don't reflect on the type of travel we most enjoy.
When I find several reviews that are particularly important for our priorities, I ALWAYS send those contributors a private message to follow-up. If they don't respond, I disregard their reviews...but almost everyone I manage to private message typically responds to me within a few days, surprisingly!
These private messages and concomitantly salient reviews almost always allow me to determine which property in any location are best suited for us, and often allow me to better choose what type of accommodation level is the best for us, as well. Often, I get other recommendations that also permit me to improve our itinerary--including or excluding sights or things that we had considered. These exchanges are more akin to those on FT for me but far more specific (exactly akin to the private exchanges on FT).
Is it work? Yes, it is--but not too much IMO and not that much more than having to read through an entire FT thread, either! I have often found that I don't need to use a travel agent at all on so many luxe trips, partly because I've had so much useful and prioritized advice from those screened travelers whose opinions are as valuable as any travel agent.
TripAdvisor is a very useful tool even for luxe trips, IMO.