I think that is what is happening to launchpad projects. I think you are right that they rise and after sometime again they drop. They are just like altcoins that they follow bitcoin bull and bear movement too. Launchpad are not separated from other coins and at the moment doing what other coins are doing, down If bitcoin start to increase then they also increase just as ICO, IEO.
That is what I am saying too, not even that they are like altcoins, they are actually actcoins, Launchpad are either IEO or ICO. Example is the Launchpad on binance, because binance is an exchange, the coins introduced through the Launchpad are IEO.
Invest on an exchange token or a dex token, they have reason to be alive, they have demanding use cases more than a launchpad project, also smart contract projects are even more demanding than ever, you can see Velas, Saito, Solana, Avalanche and others.
There are some altcoins that were introduced through the Launchpad and they were successful but just that altcoins generally can become unprofitable and very risky in a way some lead to loss.