First, you should check whether glassdoors is known and used in UAE.
For example, in my country, there are other sites which are much more popular. As a result, the reviews on glassdoors are non-representative for the companies I know here (they are actually too good). The reviews on more popular sites are, however, very valuable.
I do read people's opinions on similar sites and I write them too. I've had very good experiences with that:
Once I read that a company I applied at expected you to work 12h/day (legally only 8h are allowed in my country. I was offered the position and asked the HR about how much they worked. They confirmed the 12 h. Interestingly, they just told me about it after I asked. So if I hadn't consulted glassdoors, I would have accepted a position that I would have to quit after a few weeks or months. Basically, glassdoors saved my a** - I don't want to come across as a job-hopper.
When you read reviews for my previous company, you will see opinions that the atmosphere is horrible and there's a lot of verbal aggression. That was true and that was the reason I quit.
I once didn't check glassdoors before an interview. It was the most chaotic interview in my life. I don't want to go into details, but it was simply amazingly disorganized. Anyway, when after the interview I checked the reviews on the equivalent of glassdoors, the dominant opinion was the company was extremely disorganized.
Of course, there might be false reviews. But if you have 10+ different people sharing their opinion, you can normally understand whether there are any big red flags.