Actually there is a good amount of credible economic theory which backs the idea that localized post-scarcity markets do cause capitalist influences to wither away, and that power generation is a big fucking domino in that equation. The simple version is that maintenance of artificial scarcity is modeled as capital overhead, so there will always be an inflection point where that overhead actually exceeds the value of all other inputs. The same way eg, marketing cannot create infinite or arbitrary demand.

The other angle here is how there is often incentive for alternative commodification of abundance, which in turn incentives that abundance. This is another common model for various forms of post-scarcity capitalism. Take a YouTube video for example. The commodification of content takes the form of advertising, which effectively transfers the scarcity of one market onto another. Content is basically infinite compared to viewership time inputs. The key here is that there will always exist some forms of scarcity - and time is the big one. Art, company, leisure, physical space, etc. the model here is that eventually something like energy and physical resources might be completely abundant and effectively free, but enabled by competition over attention or leisure or aesthetic experience. You can make a strong argument that this is already happening in the post-industrial world to some degree.

The final issue is that this equation isn't unique to capitalism. Socialism mediates scarcity in more or less the same way - by transferring and meditating it across various markets using labor as the quanta of scarcity instead of capital. Indeed, many economists will argue that regulated, democratic, liberal forms of capitalism theoretically reduces to the same core basis, since "free [as in speech] labor" itself both creates the market regulation as well as provides the consumption which mediates access to capital. This is, in fact, the core thesis of "third way" market socialism, though it is obviously contentious among orthodox Marxists.