Yes they are forced to work. If you don't have a job you starve, that's how our economy works. That's a very soft form of force (specifically, a sin of omission), but it is still force.

Likewise, quitting your job is extremely disruptive and carries risk of bankruptcy if you can't get on to another employer in time. It's not simply a matter of "switch to the best offer available".

I was alive before Uber, AMZN existed and nobody starved, people just worked elsewhere, so this assertion is just not true. People have to work, but they don't have to work for AMZN, they didn't before it existed. Sure, quitting is disruptive, but people are not actually forced to work for any company, come on.

You don't think the large companies that existed before Amazon abused those workers? Wal-Mart never did anything wrong to their workers? It's a repeating playbook.

Have you seen Uber's turnover rate? Most people do quit.