I think you must not have interacted with many people who advocate for police abolition. Even just googling "abolish the police" returns a page full of results of various proposals, with detailed breakdowns. It's quite simple: just how we don't call the police for house fires or heart attacks, there are a large variety of other societal problems which would be better served by more specialized (and less heavily armed) services.

Also, police exist to protect capital, not us. It evolved from slave catching forces, and does relatively little to prevent or solve most crime.

Here's a real problem. Let's call it X. Someone proposes a solution: "Let's do Y!". It is perfectly valid criticism to say that Y doesn't actually fix X.

I don't care if that counts as "empty criticism" by your definition. If someone proposes a solution, it's perfectly valid criticism to point out that the "solution" doesn't actually solve.

>It's like the activists who say "abolish the police!"...

I would also caution you to focus less on these kinds of catchphrases and more on the crux of their message[1] (and I should point out that this applies to any kind of movement), lest you not see the forest for the trees.

[1]https://news.ycombinator.com/item?id=35346925

An empty criticism is: "this sucks, it should be improved".

A constructive criticism is: "this sucks because <reason>". 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 <reason>. Doing <improvements> would make it better".

We are very aware of why police exist.