I think the issue is the question of moderation - it's really trivial to throw up a discussion board on the web, but moderating that discussion board is where things get hairy since everyone wants to keep out the trolls but it can be hard to tell a legitimately fraudulent review from one a company claims is fraudulent - and there are extremely strong incentives to always believe the company since they've got the money.
I think the heart of the issue is that something like glassdoor gets corrupted like this then a bunch of tech folks say "Forums, forums are easy and CHEAP!" go out and roll their own - maybe a few make it big and start having to police traffic once the trolls discover them... at that point they discover that the message board portion of their product is trivial and cheap but what actually costs is the moderation of that... then the costs begin to pile up and they make some deals with some of the better actors among companies to let them subsidize policiing their own reviews and it gets normalized and then the system collapses.
It's the whole web thinking pattern. Make everything accessible, fast and free. Nobody makes money like this, and thus the system produced has no added value. It will devolve into whatever low hanging fruit can live on the inertia of branding and trends. Until someone makes an article like the one above, then someone else will try.
If I want to rant, I'd say 10 years later someone will make a real system to grade things, and it will require serious work and serious money (think about banking grades) then the system will be kept in place (to an extent.. think about banking grades).
I think the heart of the issue is that something like glassdoor gets corrupted like this then a bunch of tech folks say "Forums, forums are easy and CHEAP!" go out and roll their own - maybe a few make it big and start having to police traffic once the trolls discover them... at that point they discover that the message board portion of their product is trivial and cheap but what actually costs is the moderation of that... then the costs begin to pile up and they make some deals with some of the better actors among companies to let them subsidize policiing their own reviews and it gets normalized and then the system collapses.
Moderating things is hard.