Thats great, but perfection is the enemy of good enough. I dont think one has to eliminate it entirely, there are some niche things that are only offeres through these marketplaces. But if there is an alternative place to acquire it (starting in your community), always favor it!
All it takes is a reduction of usage by everyone to send a message. Expecting people to go cold turkey is a bridge too far right now. Kudos though for being able to do that
It starts at home. Step one is to stop participating. Reduce or eliminate spend and/or engagment with the things that are enriching these people. Doesnt have to be perfect. Cancel your prime membership. Prioritize purchases at the businesses in your community. Only buy from Amazon when you have no other choice. Get rid of facebook. Etc etc.
The fact of the matter is that the way the world is structured right now, its impossible to be 100% perfect about this. You dont have to be perfect, just do the best you can.
If everyone did this (they wont), it would affect the stock price, and that is where billionares derive their power. Even a small downward trend is enough. But your life will change in a positive way if you do this as an added bonus. In some ways life has become tooo conveniant.
The grocery store. A 99cent store. Local hardware store.