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.
I wouldn't quit because I trust in bitcoin's potential on long run. Even though it becomes obsolete at some point, it will still carry value for collectors as rarity because bitcoin is scarce, limited and the only original crypto currency among all.
At same time it doesn't mean ethereum is a shitcoin. It has the status we see nowadays for a reason and after so many years of existence, side by side with bitcoin, it's not possible to say eth's success is only due to greedy pump/dump speculative or scam schemes. There are legit professionals developing their projects through eth platform and trying to improve it even more. If ethereum were all about hype, speculation and scams it would be already dead by now and replaced by another crypto currency.