I tend to agree with this line, and it seems to address the question effectively.
Many altcoins attempt to do too much or introduce overly different features, which can result in technical problems or a loss of focus, especially since some lack real utility and see price increases made by community hype.
While certain altcoins depend heavily on a small team or a single founder, if those individuals depart or lose interest, the project can eventually die or ultimately fail on its own.

While Bitcoin has hundreds, if not thousands, of developers.
Being open source, it attracts more developers than any altcoin, but Bitcoin will never kill altcoins.