I use TA reviews for most places I'm looking at staying simply beacuse they are more likely to have them listed than anyone else, when they are elsewhere I check those too.
It's simple really, be wary of any member who has only posted the once, or a few times, & has done a glowing or scathing review, not to mention several that are worded very similiarly with the same grammatical errors. Once the likely false ones are weeded out & ignored it's the same as anywhere else. BTW, these can be reported to TA & with the massive membership & volume of input on there you can't possibly compare their vetting procedures to a site like this, there is bound to be more automation & a lower level of personal scrutinisation. I have had success with reporting such issues in the past, there was one place I knew very well & a whole row of similiarly written 'reviews' were obviously false, several comments made it obvious that they had never set foot in the place. It is now red flagged, telling readers to be aware.
Read the bad ones as to what their 'problem' was, it's often due to unrealistic expectations or about something that wouldn't bother most people. Take an overall view, not just pick up on one particularly good or bad report to make your decision.
I would do the same with any site with reviews, even here, because what one person thinks makes a resort/hotel/restaurant etc wonderful would probably be my worst nighmare & what some see as a downside may be what I'm looking for. It is all only opinion anyway. You are the one that makes the decision in the end & if you only rely on one place or a couple of reviews to base that decision on that's your choice.
Back to the subject of why people don't use HT any more. Boring comes to mind for anyone not going on a package or to the main tourist resorts. I have been happy to post detailed replies to people asking a bit beyond that & would love to be able to more often, but those wanting that sort of info don't seem to frequent this board.
The above is relating to Greece, flights only, city breaks & this forum, I don't look at other destinations.