There will be no such era.
Most completive systems tend over time to reduce to oligarchies or oligopolies. Cars, breakfast cereal, pop, cosmetics, etc. The industries often start with a great many companies doing things very differently, but over not too many decades that changes.
Just look at the shelves of your supermarket where two or three companies make most of the products in any general category, despite all the names and packaging.
Advertising is one of the things that differentiates these products, advertising that plays on minor differences of scent or color or herbs.
We get choice, but not much in the way of extreme choices. New products are lucky to be boutique items given a tiny shelf space.
Politics is no different.
Indeed, advertising only becomes more important every year, raising the cost of politics and reducing the genuine information offered.
If you know a way to turn this around, you will be a hero to democratic values, but pardon my skepticism.
