Well that's true I invested before to ICO multiple times especially on presales and what happened is that after hitting the exchange the value of my investment almost reduced up to 60%
No, not only ICO alone because 97% of all new coins are hype base and the coins usually experience dump when they are listed on exchange but if the team involve have good strategy to help the coin surge in price the coin will be save thats what Uniswap does about their UNI.
In case of UNI, the team has a lot of Big company as backer for funding the Exchange during there experimental phase. They don't have any ICO and just airdrop there token to exchange user that's why they can maintain the price because the token is spread on investors unlike ICO that whales are buying the majority of supply during Presale and private sale that result to easy manipulation of the price.