Altcoins are definitely needed as an alternative to bitcoin. It creates a healthy Bitcoin competition. Most likely, if there was a monopoly in cryptocurrency, then the price of bitcoin would continue to grow. And to what extent the currency would rise so far is not known. Altcoins restrain growth by developing more interesting and promising projects.
altcoins arent created to compete with bitcoin or to provide alternatives. They're created mostly as tokens on a very specific network, on which bitcoin cant operate