Here's a more complete, if a bit dated, analysis.
https://www.law.upenn.edu/live/files/6611-report-municipal-f...I would say that Greenlight in Wilson is still fast because of the relatively recent infrastructure build out. The question of whether they are stagnant are not won't be answered until the next build out is required.
The project was financed by bonds with the infrastructure as collateral. Since Wilson's bond has a balloon payment due in 2033, any new infrastructure would probably require rolling over that debt in addition to the new infrastructure costs. Given the low positive cash flow, it remains to be seen whether they will be able to keep up with future infrastructure demands, whether driven by streaming VR or other services. They are also deriving significant revenue from cable television and landline phone services, both of which are potentially negative growth service areas over the next 15 years.
The peculiar advantage of municipal broadband is that municipalities are usually not rural, they can take advantage of the higher density installation locations which most providers want. Many of the monopoly contracts issued by various localities to providers came with the caveat that everyone in the county needed to get access to the service. To be fair, the higher costs for more rural installations should translate into higher prices for rural customers, but that would reduce demand.
So, it is certainly worth trying more of these muni-broadband projects, as this obviously is not yet a solved problem. My only plea would be that we don't give anyone a monopoly on putting wires in the ground, whether a private company or a government entity, whoever wants to safely lay cable should be given a permit.