Price fixing is temporary, and doomed to fail in the long term. Nixon tried it with an Executive Order and it was a disaster, causing supply chain constraints and prices shot well past inflation when the Order expired.
Congressional legislation setting grocery store presentation limits would increase brand variety, foster competitive pricing, and put an end to the corporate control over pricing.
Limiting the number of products and facings in a store by percent of available retail space.
Limiting the number of products alone doesn’t suffice, because larger companies will pay retailers to increase the number of facings of a product to keep out competition in that product space.