In my opinion, if the old coin is from an ICO project, then it is not worth buying and keeping for the long term. Many coins from ICO projects do not survive and are of no value in the long term because they do not have strong fundamentals. Some even went missing on the exchange after a few months.
it doesnt matter about from ICO or not , but we talk about project quality . Is it continuely build the thing in their roadmap or not, if they did it and then check gain its progress. This what we are talking about while analizing project , no matter if come from ICO , IEO or even IDO.
in my view the current altcoins are the ones that have good popularity will be the best. Examples such as Dogecoin have recently been named to become popular among cryptocurrencies and made the price of Dogecoin increase by ElonMusk (Tesla CEO). so now altcoins have their own era. so new and old altcoins have no effect on altcoin enthusiasts. because popularity can provide greater benefits.
doge coin get new investors or new community member since elon musk shill it. And actually doge holders was a fanatic man , the hold it for long term since price below $0,1 Doge come to new era which is utility was not needed .