The reason old Bitcoin Maxis went to Alt-Coins is because the Maxism wasn't in a specific brand but in technologies.
People chose alt-coins that better serve the purpose, and utility they want.
Bitcoin was a proof of concept for decentralized digital cash, and it was so successful it helped make projects that are better versions of Bitcoin.
Like any other technology it's meant to grow, and innovate.
So in all reality, if you want to be a Bitcoin Maxi, you should actually be an Alt-Coiner too.
Because innovating on the idea of Bitcoin is what helps Bitcoin grow.
Vitalik Buterin used to be the biggest Bitcoin Maxi before making his own "Bitcoin" Ethereum, a smart programmable currency.
That idea innovated upon Bitcoin's vision, and made what possible in Bitcoin grow even more.
There's so many features that could be added to Bitcoin due to the work of Alt-Coiners but isn't because dogmatic people nowadays see changes to Bitcoin as a threat to their fiat bags.
Bitcoin is meant to free the individual from fiat, not trap them in a vicious cycle of fiat thinking.