One problem can't solve from first, if new investor can't trust new fresh coin why they don't invest in old coin. We several good coin already exists in cryptocurrency even with very low price. Even I don't think there could be a trust problem. All solution is now is the correction time!!
But most of the old coins are shitcoin derived from recent ICOs. From 2018 to now, I have not seen any successful ICO project. Previously, 2016 and 2017 both have lots of great projects and it is appreciated now. Decred, Nexo, Waves, NEO, etc., now projects are only good at planning but can't do it. That's why investors now invest only in old alts.