It's an interesting point.
My counter to that is that XR are only listening to, and being driven by, the wide scientific consensus on climate change. Across the world, scientists are telling us that we need to drastically reduce climate emissions in the next 10 years.
Unfortunately, encouraging everyone to ride bikes isn't going to achieve the level of change needed. We need systemic change at governmental level. XR is putting pressure on governments to make the kinds of change that are needed.
To your comparison with preppers, the difference is that XR are actually trying to avert the catastrophe, not just preparing for it. Also, rather than being faith based, a worldwide consensus of scientists are telling us that the apocalypse is coming, but it seems that XR and groups like them are the only ones listening.