You are making a lot of strange assumptions. The majority of EGS store games so far are single player indie games. They aren't going to pursue a strategy that is similar to propping up the next GaaS title. There's already PR companies that do this. Do you think the devs of Dawn of Man started at Ninja and then lucked into finding strategy streamers? No, they focused the people they know would actually enjoy it and have fans that would.
They'll likely do what you are suggested for say Spellbreak (and already did IIRC), but both publishers and Epic know that the way to sell Outer Wilds or a dungeon crawler RPG like Operencia is not to court Dr Disprect.
The purpose of EGS is not to create the next Fornite, they already have that. You are acting like a company like Epic and publishers like Team 17, who have managed to turn turds like Hello Neighbor into hits are just going to flail around in the dark.
I just don't see streamers as viable and sustainable way for indie developers to promote their games.
Hello Neighbor success was due to flailing in the dark. It was just the perfect Streamer-bait game in a period without that much Streamer-bait game.
The main issue with games and streamers is courting the wrong ones. Most games try to court the big hitters instead of focusing on the ones that actually matter for their game. Big streamers are never going to be the first one to jump into your game (unless you really pay them) because they are making a lot more money in their current set-up.
Small but focused on a genre streamers are the ones you should court and try to get on your side. If you involve them from an early option, they will play the game because they enjoy it and because they know their audience will enjoy it, creating for a long lasting success (instead of a 1 week explosion of support followed by an instant drop like in most paid services).
TLDR: a succesful indie should focus on catering to the core audience of their genre and build upwards from them. Trying a catch all strategy from the beginning normally ends with most of the core audience not caring that much and not catching too many people from outside of it. Catering to the core audience also tends to give some interesting feedback that can improve the game during development.
A successful strategy is more similar to Paradox or Hollow Knight than Spellbreakers.
Edit: Also yeah, streamers should be only a part of the strategy. Focusing your game on streaming is not a solution for short story focused games because the main draw of those games is the story.
Even for game focused games, there is more work you have to do than focus on streamers (the Dawn of Man game was a success before the streamers jumped into it, because it was the FANBASE who pushed/recommended the game to the streamers!).
