Excuse my ignorance, isn't this a technical challenge, rather than the idea in itself was stupid?
Isn't that saying shooting sky full of satellite for communication is stupid until SpaceX made loading anything to space 10x less expensive?
I would say the idea isn't worth trying because it clearly wasn't ready, ( I mean if napkin maths already show it is off by a factor of 10 than it really is stupid trying it ) but I don't think the idea in itself is stupid at all.
The thing about solar roads is they're covered by cars, and they don't work when covered, for obvious reasons. Then all the road dirt, grime, tire dust, oil, etc, builds up on top of them blocking the light for good. The road is about the worst thing you can possibly try and generate solar electricity from.
edit: I'm all for trying crazy moonshots. Just not down right idiotic ones that are pushed by pseudo-science and clickbait activism [1].
[1]https://www.vox.com/2014/5/14/5717036/should-we-cover-all-ou...