Sure, old coins cannot be neglected, because they still stand strong and lively. And whenever you make mention about the crypto world, you must surely make mention of them, BTC, ETH, LTC etc. They made the popularity of crypto. New projects are just building on the foundations already laid.
As of popularity and price changes, the old coins has gained a lot and they have made profits for traders and investors over the years.
New projects likely suffer pump and dump, though they also make profit for investors but when they haven't gotten the stability they need completely in the market, once they're dumped, the even get delisted from exchanges. However, we still see some new projects that are successful and still waxing strong in the crypto market.
But the old coins can't be forgotten because once upon a time, they were also new coins in the crypto world.