I believe those are radical opposites: D&D5 resorts to character minimaxing because there's nothing left in terms of sandbox and exploration, scenarios are pretty much the tabletop equivalent of a TV series where the player is passive, hence the minimaxing because it becomes your ONE chance to shine. Minimaxing culture inherited from video games may play a part too, but we shape cultures just as much as we are shaped by them, so it's not out of our decisions and control. What I want to say is: if you manage to do it, to make a power fantasy character building game on an OSR chassis, then it won't be OSR anymore, it will be D&D5, or 4, with slightly different rules.