For profit utility participants are desperately afraid of their return on equity being crushed by the new energy model, hence the need for strong political response from the citizenry. The grid can absolutely operate in the manner you describe, but profits will be diminished and investors will struggle to reach for previous profit potential unless you're in a non profit config (coop and whatnot).

Shades of "The Innovator's Dilemma" and what not. Incumbents do not care for their gravy train being taken away.

Edit: https://www.eia.gov/todayinenergy/detail.php?id=40913 ("Investor-owned utilities served 72% of U.S. electricity customers in 2017")

> Investor-owned utilities, or IOUs, are large electric distributors that issue stock owned by shareholders. Almost three-quarters of utility customers get their electricity from these companies. IOUs are most prevalent in heavily populated areas on the East and West coasts. In 2017, 168 IOUs served an average of 654,600 electric customers. The two largest IOUs are in California: Pacific Gas and Electric, with 5.48 million customers, and Southern California Edison Company, with 5.07 million customers.

So... exactly what the OP said?: They can't take any more solar input. They need battery I/O.

No, not exactly. "the era of sending excess rooftop solar generation to the grid is over" is the OP's statement I disagree with. "They can't take any more solar input", yes they can, by adding more grid battery, which is currently happening.

Where are you reading that. the poster literally said "Worth noting that there isn't a lot of room for growth of solar that isn't battery-backed"

> Worth noting that there isn't a lot of room for growth of solar that isn't battery-backed. California exports a ton of energy during the bright months. As a practical matter, the era of sending excess rooftop solar generation to the grid is over.

They are referring to the last sentence in the paragraph you referenced.