It likely doesn't make sense to talk about "democracy" as a single concept. There are many different types, each with pros and cons. The USA is a outlier in terms of style of government, there aren't really other "democracies" quite like it.
Here in Canada we have a variation of British parliamentary/representative democracy. It has issues too, but IMO generally works a lot better because power is not concentrated with any one person or role. It forces compromise.
When we look at scales we also need to change our ideas. Democracy can work at large scale, but it certainly won't be the same structure as at a national level, or a municipal level.
In countries where we see it going awry (i.e. Turkey, USA, UK), it is more complex than just the system of government... although the system is certainly a part of the issue. As @jasonw22 mentioned, journalism and education are core parts of a functioning democracy. Without these things it cannot work. And it's pretty easy to argue that those things are deeply and fundamentally broken in all the countries mentioned.
At the core of any democracy needs to be an educated electorate, open access to information, and a way of holding elected officials accountable for their actions (more than just the fear of not being reelected).
All of these systems are basically gone in the USA, Turkey, and more. It's a recipe for disaster, which we're seeing play out very quickly.
IMO, if we want to fix the government we need to start with the citizens. If you look at examples of high functioning democracies many of them have free higher education, health care, and more. That's not a coincidence.