Its impossible to have one or two coins in crypto space because one or two coins can't solve all the problems we have in this world in every aspect of technology or others, if you want to keep a coin for a long time make sure the coin or token solves one or two problems in crypto space or the world, this type of coins don't die easily because they have real use cases, its simple as that
Yes they do exist for a reason but problems are existing not because they cannot be eradicated but because they are continuously occuring to the point that we thought that we solved it but another one would occur. There is no such as perfect, everything has flaws. Even bitcoin that some people think its perfect but other alts occur to fultill bitcoin shortcomings. Solving problem either one or two or more than three won't satisfy majority but rather would be cap to fill a hole. Besides alts are created for one clear designated purposes.