RTS did go mainstream and it indeed turned into games very different from old school SC et al.
Plants vs zombies and LoL are the descendants of the genre and are or at least were, HUGE. Tower defense and moba are the two evolutionary paths that RTS took.
Tower defense is super mainstream, but moba, while huge isn’t really mainstream in my opinion. But one things for sure, they don’t have much in common with SC except the lineage.
How many games game out this year? Thousands. There is absolutely zero possibility that MS or anyone else is anywhere near holding monopoly status on the production of entertainment software. Even if they bought EVERYTHING new creators would enter the space the very next day.
The competition! lol! Activision is going to put out 2 games this year. Whatever will we play now that these 2 games are owned by a platform holder?
You are correct though that there are a million cool ass games you can play right now and put your money in the pockets of people who make THINGS instead of people who make value for shareholders.