The moment you go protest something the government or a company is doing that's ethically or morally wrong or disadvantages the working class, you get beat up by police and thrown in jail. How is it different?

Because that doesn't happen as a rule. Sure, sometimes it happens, especially if the protesters are violent. But, it's perfectly normal to have an anti-government protest where the cops just stand and watch. Look at all the No Kings protests in the US, and how almost nobody was beaten up or arrested. Millions of people out on the street protesting, only a handful of injuries and arrests.

Or if you talk bad about a company you get sued for slander for millions of dollars to shut you up.

Which also only rarely happens. When it does, you can defend yourself in court, and sometimes if your case is a big one the ACLU or EFF or someone will step in on your side to help defend your right to say things. Compare that to an autocratic country where critics of the government or businesses that are cozy with the government often simply disappear and never reappear.

But, none of that is really what makes an authoritarian government different. What makes it different is that you can't change that government. Modern western democratic countries that use a mix of socialism and capitalism (so, all of them) have elections. Those elections may not always be fully free or fully fair. But, they exist and they're not just for show. Surprise results happen. People who have no connections to money or the establishment sometimes gain power. In authoritarian systems that simply doesn't happen. There are sometimes struggles for power at the top. But, the ability for the people on the ground to influence the way they're governed is extremely limited. It's what defines an authoritarian government.