Crypto can exist without CEXs. But let's not forget that the growth of this industry is deeply tied to CEXs, and it would never have reached its current position without them.
Who cares! Bitcoin will still be existing and there will be pump and dump coins. You can read what OmegaStarScream has said about the matter.
Lots of people are saying XMR but that probably not going to survive "if every CEX" dissapeared. If major CEXes then yes sure, XMR has proven itself in that regard. But no CEX at all? XMR has barely a DEX as far as I know, very few sites uses atomic swaps.
I'd expect BTC, and pretty much every EVM based coin to survive given they all can be listed on DEXes. Obviously the prices would be affected though.
Monero increased from $100 to $800 before falling to $350.
Cryptocurrencies can exist without centralized exchanges.