It’s increasingly likely the grid will get torn down and replaced by cheaper rooftop solar and batteries, because of the costs described in this article. Tony Seba said in 2014 that power grids would be uncompetitive once solar and batteries got cheaper than just the cost of transmission:
Why is this important? Because in most developed markets, the cost of electricity is comprised of two components. The cost of producing the electrons (power plants making the electrons) and the cost of delivering the electrons (maintaining the transmission and distribution lines). Each one accounting for approximately 50% of the costs.
God Parity happens when the cost of producing electrons (via Solar PV) and storing them (via batteries in and near your building) becomes chapter than 50% of the cost of today’s utility-provided electricity.
Why is this important? Because in that scenario, even if one produces electrons for free (via nuclear, fusion, etc), the locally produced and stored electrons will be cheaper than the cost of delivering those free electrons and therefore cheaper than nuclear/fusion electricity.
Given that the cost curve of batteries is following a very similar trend to the cost curve of PV solar panels, this will happen sooner rather than later.
In Australia, this is already happening in the more remote areas with poles being replaced by solar and batteries, and the utility death spiral is now hitting Pakistan and South Africa’s inefficient grids due to very cheap solar.
Reticulum is in its infancy and does what you describe (and can use any communication medium), but that kind of separate intranet system is difficult to search the way the Internet is. It would be like Discord where the inability to search it (unless you have already joined the relevant Discord) makes it hated as a replacement for forums.