Please ELI5 – Thank you

Hey, I have a question regarding Ethereum 2.0, I apologise if it's been answered elsewhere but I have been hunting around for 2 hours now and can't find a satisfying answer

Is it true that once ethereum2.0 is launched, it's adoption still requires the consensus of the vast majority of holders? Is it possible that a few significant members of the community reject ethereum 2.0 for some reason, and create a situation where ethereum2.0 just is a fork off of the main coin like bitcoin cash?

All I see is stuff online that says existing holders will have nothing to worry about, and their existing ETH will be the same with ethereum2.0, but what if a significant amount of people do not migrate, and prefer "the devil you know" with ethereum1.0 and it's proof of work versus ethereum2.0 proof of stake and sharding which is arguably much more complicated, and something new for people to learn

Thanks – I hope my wording makes sense!