It dominates because it's the one that everyone knows. If you're lucky enough to find a shop that accepts crypto it's almost certain that the crypto they accept is bitcoin and bitcoin only. despite its flaws it is a proven technology. It might 3 hours to send an on chain payment but you don't have to worry about a technical glitch dropping it.

I somewhat agree about it being not great though. it has serious scalability issues that were supposed to be addressed by lightning but lightning adds a lot of complexity imo. My grandma is never going to be able to figure out how to use lightning whilst still being able to benefit from a self custody wallet.

A lot of the newer coins that crypto bros bang on about seem to be centralized under private entities, "regulation friendly" and not distributed.