"Gadgetbahn" is a derogatory term in transit planning and advocacy for transit methods that require overly innovative technology, often with no clear rationale. This technology is often theoretical, and is a solution in search of a problem. It also often depends on a gee-whiz factor, with futuristic aesthetics or tech industry buzzwords. There are a lot of autonomous pods driven by neural net AIs in gadgetbahns, and if you aren't sure what those words mean, neither are they.
Many gadgetbahns are reinventions of basic concepts like "train" and "bus" that already exist. For example, take the example of autonomous vehicles that have separate lanes. Well, as long as you have an autonomous vehicle, it makes sense to make it a little bit bigger (for peak demand), and lower the floor for quick boarding and accessibility. And as long as it has its own protected lane, maybe it should have some sort of track to limit friction and increase speed and efficiency. So now the "autonomous pod" has become...a train, or trolley. Ideas we have had for a while.
Other ideas are ideas that make sense in certain limited circumstances, such as telefericas or funiculars, but that make no practical sense in most cases. Medellin, a city with dense neighborhoods built on steep hills, has an innovative system of telefericas. But such a network doesn't make sense in say, Cincinnati, except for, as mentioned the "gee-whiz" factor.
For complicated historical and demographical reason, people in the United States often have an aversion to mass transit. While it is not usually explicitly stated, one of the reasons for gadgetbahns is to remove the stigma from mass transit. People who might not ride a bus might ride an UberXTendedAIPod or whatever, because it is aesthetically different and marketed better. And while some of these ideas might make sense, they don't really change the basic attitude and planning situation that have led to the US being transit-unfriendly.