On one hand, Itch.io is supposed to be for indie games and while I personally have not got any experience with their platform their model does seem to be pretty incentivised towards developers if the only thing those developers care about is getting more profit from the games they are able to sell.

However, on balance, indie game developers don't often have the budget to create the kind of hype around a game that would push most consumers to buy it from just itch.io. So it's in the best interest of lots of indie developers to make their game as accessible as possible and go where the users are.

In that respect steam (and Microsoft and Sony) are the places to go. Of those three steam has less active competition from their company for games than either of the other platforms. Indies aren't competing against Valve games the way they are against Sony or Microsoft produced games on the relevant platforms.

At this point I've backed 4 games on Kickstarter or in one case the developer site, and I am very happy with each of them. They have (all except one) offered keys on steam, Microsoft, Nintendo, and Sony. Even when they didn't release on all those platforms at the same time. Two of them I have purchased on a separate platform after receiving a key on my chosen platform so I can play those games in multiple places.

On the other hand, I don't necessarily like that Indies probably won't see the same benefit of paying less per unit served after selling $10 million and again after an additional $5 million (Valve drops their percentage from 30% to 25% after a developer sells $10million worth of units and again to 20% for every copy sold after selling an addition $5 million sold on steam).

This I feel is a boon to big development firms that not a whole lot of Indies can take advantage of. So there is definitely room for improvement there.