After the announcement from Poloniex, each of the cryptocurrencies faced a major price fall. Some of these coins have lost 30-75% of their price in just a couple of hours. Traders and the community were shocked with the list of coins delisted and the fact that there are no explanations of why Poloniex decided to do it.
If 30-75% of your coin's price depends on being listed or not at the "pump and dump platform" Poloniex, then your coin is dead or at least deserves to die. These coins have no reason to exist if it were not for the "developers'" profit. There may be some forum posts of some whining bagholders but if you don't like this, then don't invest in this kind of coins.
And if a coin is really alive (like it seems to be the case with CureCoin) then a delistment on Poloniex shouldn't have any effect on the coin's health - only that there will be less pump-and-dump games.
I agree with you, there should be no artificial maintenance of the coin's life. The coin should live thanks to the demand and popularity of users. Poloniex just got rid of unnecessary and dead coins