It implicitly and falsely assumes that everybody will agree on what the solution is. In the presence of differences brought on not merely by "false consciousness" but by legitimate differences in opinions and desires, it fails the basic Kantian imperative to not do something that breaks society if everybody does it, because it means that everybody who disagrees with some policy, which is always somebody, should try to break things, rather than fix things. In the local vernacular, this "scales poorly".
(I am really tempted to say that Marxists are prone to this, but it would be an over-specific adjective. Truth is, almost everybody "knows" that deep down, everybody else is secretly really like them, and it's just a lack of knowledge or external influence that leads to apparently disagreements. However, the evidence overwhelmingly contradicts this belief. Even in the presence of hostile external actions or lack of knowledge, well, how do you know that you are not the one lacking knowledge or subject to external influence? And many people's value systems legitimately differ.)
