The Outline has a great story about outsourcing in game development, starting from the (great) PS4 exclusive Horizon: Zero Dawn. It shows how much of the development of games takes place elsewhere, but the most important quote for me is
The Dutch newspaper NRC Handelsblad reported Horizon’s budget was more than $47 million, the country’s biggest media production of all time, though that doesn’t take into account the money Sony spent on marketing. In the same year, it would be surpassed several times over by non-console games. Player Unknown’s Battlegrounds generated more than $400 million as an early access game with only one map, and mobile juggernauts like Tencent’s Honour of Kings pulled in a little under $500 million a month from a player base of more than 200 million people.
Making high quality, polished, long-form games has become economically untenable, or at least not as profitable as going for mobile games. Why spend 7 years making a huge open-world game when you can make a Farmville or Clash of Clans ripoff?