Technology

I don't personally, but it is another proposal, that's why I mentioned it. There are some parts that seek decent but I have not read up on full explanations enough to understand the theory behind it.

The question was very open and there's a lot to explain, so sorry for the text wall I ended up making

As for keeping stuff "on the rails," more or less just more of the stuff we should be doing to try keep capitalism on the rails. Regulations and regulatory agencies and government bodies, and better electoral and government systems. And on top of that, the workers being in control will eliminate a lot of the motivations for businesses to do 'bad' things. Treatment of workers and profit distribution most obviously, but also things like quality of product or service, because the workers are also likely either direct consumers of it as well or more closely linked to direct consumers.

As for government and democratic improvements, since I'm assuming we are comparing against the US, we have a pretty shitty democratic structure and even governmental structure to some extent. First and foremost, the two party system and first past the post voting. Systems like ranked choice allow for a much broader set of parties and corresponding values to be expressed in governance. Other things like how shit of an institution the Supreme Court is, the electoral college, etc. A more European democratic model is much better. Also, a great example of how Europe has an much better control on capitalism is to look at how a lot of tech and internet protections and regulation is almost exclusively European. Things like requiring all devices to have USB-C, all of the GDPR which is the giant data privacy regulation that requires things like letting users obtain a copy of all their data, and also delete it among many other things. Also something I've seen recently is that by in think it was 2027 all smartphones will have to have removable batteries which is amazing.

Basically democratic socialism would be taking all the good stuff Europe does and cranking it up to 11, plus a few other things.

Edit to respond to your edit: perhaps, but how does a greedy person then get elected? The whole point of democracy is that you elect people who represent you, and also have checks and balances in place to limit any given individual or group from overstepping their power, a can be removed if they are causing harm.