Glassdoor could be a good source of information for prospective job applicants, but I shouldn't be forced to leave a review or a salary to see the information. Anonymizing the reviews doesn't help - there are six people on my team and I'm the only person at my company with my job title, so it would be obvious that I'm the one leaving the review.
People will leave reviews and salaries of their own volition once it's safe to do so and if they really have something useful to say about the company. Conversely, if they are forced to leave a review, they review will likely not be thorough or helpful to anyone else. This type of gatekeeping was a bad move for Glassdoor.