There is a lot of shilling lately (again) with "the flippening" event happening. Ethereum has created a new market which is basically 99% scam tokens, rugpulls, pump and dumps and NFTs which are probably used for money laundering. Anyway, the thing is, there is definitely if a demand for all of that, even if it's all based on a platform that's not decentralized.
So to the point: Would you quit if a centralized shitcoin managed to surpass Bitcoin in marketcap? At that point it would be clear that entire space is a joke. Bitcoin would still march on as usual, but it would be just sad to see people putting their money on shitcoins rather than on the only actually decentralized blockchain worth anything.
It's actually hilarious to see someone get so twisted up that another cryptocurrency might one day take the crown of Bitcoin. It is actually almost inevitable that another cryptocurrency will unseat Bitcoin because the sheer low number of coins - a max of 21 million (some of which are being lost all the time) is a great restriction and will over time make it harder to use as an effective currency. It'll be great for the current holders but people will simply move elsewhere, even if it's just a psychological thing - people would prefer 1,000 units of a stable currency than 0.0001 units of a slowly increasing currency. There is enough room in the market for lots of people to get richer, so don't fret over other coins creating competition.