Earlier quoted context omitted.
Having a solution is not a prerequisite for providing criticism. It is okay to see a flaw but not yet have an answer.
No but it makes it an empty criticism. It's like the activists who say "abolish the police!" but either have no insight into or are deliberately ignoring why the police exist, and have no ideas regarding who would perform the equivalent function instead.
A constructive criticism is: "this sucks because ". It is constructive because it may not be trivial to explain why something sucks, yet it is mandatory if you expect to find a solution.
A solution is: "This sucks because . Doing would make it better".