Now, altcoins are competing with ethereum and not to bitcoin anymore. The best example is CARDANO. It seems that since they cant destroy the king, they are now targeting the queen and wanted ETH to beheaded. All those altcoins always claiming that they will replace either BTC or ETH where in fact, they simply following its footsteps but only limiting or avoiding the same mistake happened to ETH or BTC. By the end of the day, they are only copycats and the original will still remain on the front line. Those claimers will forever become a follower of front liners.
It seems to me that you are right only in part because old coins are good, but the market is very young and promising in terms of technology. New coins have huge opportunities for technical development - for example, sharding, which Zilliqa and Quarkchain try to realize this year! Perhaps, such new technological projects will become the basis of a new wave of technologies and will outstrip Ethereum and Bitcoin in the near future!