A Crypto project is a venture where the future ahead is uncertain, there is a possibility that a cryptocurrency project will fail after several years on the market. Hackers are relentless attackers, so any Crypto project can be a victim of a hack that can turn its successful years to ruins. Aside from that, project developers are also human susceptible to errors so it is also possible for a top project to crash due to mismanagement. There are also recorded history in the financial industry of top company getting bankrupt because of mismanagement and certain events.
Not always but sometimes there are exceptionally promising altcoins being launched every now and then that can make some of the projects on the top 20 altcoin move down in their rank.
I totally agree, a new project now is usually a new technology, unless of course it is to be on the first coin list. and as long as there is a market, there will always be something better than before... it's evolution, natural selection.