I think the OP is half right - we are getting a lot more innovative games than the last half of last gen, but it isn't because mid-sized games can succeed again, it's because Indies can now make Mid-sized games!
Think about it. No Man's Sky is absolutely massive and looks like a modern game, recent advances in programming and graphics have made it cheap enough to obtain great graphics that now even indies can!
Someone else saw the light. Thank you.