Free markets are simple and the “they” are two parties the buyer and the seller. Much of the problems we see with lousy service and high prices is due to monopoly agreements between local governments and last mile providers. Your local internet provider faces no competition.
True enough but that is not the issue here. The question really is "who should pay for the added infrastructure required to support the ISPs higher Netflix bandwidth requirements?".
The ISP wants customers. Customers want 4K. Netflix wants 4K. The ISP can't provide 4K without added hardware, software and people. Who pays?