There's a difference between a producer appealing to the mainstream(producing for the bigger audience) and selling out(forgetting artistic integrity for the sake of monehz), and consumers tend to accuse artistic producers of selling out whenever they make something said consumer doesn't like (Which I would say is what is going in several of your examples and most of game theory's vid, just so you know game theory is generally a pretty yellow source of info on the gaming industry). Also note that the mainstream is different for each industry and the mainstream of each industry tends to change drastically every few years. 

As far as the movie, music, and television industries go, they've always been heavily connected to the mainstream as they were born alongside widespread media (which created the mainstream), but we've definitely had more producers full on selling out in the past decades. The main problem now is that the mainstream's taste has been degrading since the late 90's and it just terrible, to the point that we're left looking for maybe one good movie each year instead of a competition as to which will be the best. You or any of the countless masses who have made similar "Don't buy garbage" speeches online do not have any chance of doing anything to change this, the only way this will change is if the widespread media starts changing the mainstream for the better, which it doesn't look like it will do for at least another several years.

As far as the gaming industry goes, I'd say things are a bit different. The gaming industries has always have very loose ties with widespread media with only occasional games getting picked up by it (WoW, Minecraft, and CoD are good examples of what a ridiculous money maker the gaming industry could be if widespread media gave it more attention). What I think is the cause of the problem you are talking about more has to do with one of the recent major mainstream changes, in that when it changed a large portion of the consumers didn't go with it, which has created another large (but still small compared to the mainstream) faction that detests a good portion of what the recent mainstream likes. Game companies had to make a decision as to which group they would work to appeal to more, most chose the mainstream while this little company by the name of Valve has made a killing by playing Steam as the savior of this other faction of gamers. IMO most game producers haven't full on sold out, apart for EA who sold out a long fucking time ago 

As far as trending and franchising goes, yes, they're cheap tactics used to milk the mainstream, but major production companies gotta get their money somewhere. Though several of the things you accused of just following treads have been a thing long before they were popular. You say superhero movies weren't a thing and got no respect, when really big groups have been producing superhero movies and show long before recent series made it epic-tier popular. Oh, and as someone who didn't like Hunger Games, I'll tell you it is just as guilty on all of that teen-book trend shit as all the others, if not more so than most as it is the major series that took the mantle once Twilight and HP were out of the way.