Criticizing in a vague way is a great way to make a broader point if people already agree with you.
If they don't, then it's completely unconvincing because it doesn't actually provide any new information.
So if the goal is to gripe to other people who "get it", then sure, vague criticisms are great.
If the goal is to convince people that something is an issue, then all vague criticisms do is establish what your opinion is; they fail to actually provide information that could (justifiably) convince anyone.
At best, they can convince someone to be interested enough to look into it on their own.