only one person takes out the loan

No, a group of people would form a co-op, just like how people form a company, and the co-op would take out the loan. Entities can take out loans just like people can

but this is the same as all of the employees having stock in the business

No, stock is transferable and sellable, and not equal. If every employee got stock then one of them could / would sell it to someone with cash upfront. Now that new person is now getting money from the business without contributing any labor. They can then use that money to buy more stocks and make a passive income off the company. This leads to capital accumulation and a class of people making money off other people's labor just because they have more money, or had more money at the start.

As for Amazon the average employee would be making a lot more then they are right now but they wouldn't be billionaires. Billionaires never make there billions off working, they make it off capital gains, and since the shares aren't sellable, and thus have no monetary value, there'd be no idea of capital gains for a worker in a co-op.

For the restaurant example I agree they may want to start a business for economic security, but thats not the same as getting rich. Economic security can be provided by a social safety net.

I also agree they may want to start one because they lack autonomy, but I'd say that's largely the result of the alienation of working in normal stock owned companies where the owners make the decisions. If you are working in a co-op and get to have a say in all the decisions that alienation is partly ameliorated. If you want a hand in more decisions then you can "run" for a managerial position and get elected, administrative work would still be necessary in a co-op.

For the communist question most communist countries were more equal then the capitalist countries before the cold war ended. They were poorer, that's partially due to inefficiency, but also due to the fact that most of them developed later then the capitalist countries there often compared to. If you look at one of the last hold puts in Cuba it could be argued that the quality of life for the poorest there is better then the poorest in the u.s. as they have better access to food, housing and healthcare. I'm not going to defend the oppressive political regimes of those countries, but the standard of living wasn't as bad as a lot of people make it out to be.

Could you explain what financial risk is still there if you make an LLC? My understanding was the whole point of an LLC was to guard someone's personal assets from risk if the company goes under.