Unfortunately, that cuts both ways. There are a lot of ways to be exploitive, to your and your customers' benefits, when you're a $113 B revenue/quarter company, that simply aren't available when you're a startup.
Hell, Walmart pioneered the "How'd you like to sell in our stores?" + "You need to reduce prices, or it'd be a shame if we, your biggest customer, had to drop you" two step. And Amazon pioneered hyperscale logistics efficiencies. Both of which only work if you're giant.
If we want a return to competition of yore, I think it's only going to happen if we (a) prevent "extra-large" companies from having in-house logistics & (b) prevent predatory contracts and pricing when a size disparity exists (e.g. Walmart/supplier).
And given both of these are pretty fundamental to the way many companies work, I'm not even sure they'd be feasible.