In the market, there must be various coins. If the market only there is Bitcoin I think it will not run. Bitcoin needs an Altcoin because if there is no competition, the market conditions that I think will be empty.
I don't consider altcoins to be a competitor of bitcoin as I haven't seen even one project that could out perform bitcoin both in adoption and trading. Ethereum showed some positive signals but when it comes to trading and gobal adoption, bitcoin still outperformed ethereum although in utility, ethereum is the no1 blockchain. Libra could out perform bitcoin as no1 most trading coin just as Tether is trying to achieve but that's a story for another day.
The altcoins market should compliment that of bitcoin instead of been competitors that's why I'm emphazing both coins are needed for a faster and profitable growth of the cryptocurrency industry. Altcoins providers utility while bitcoin provides global adoption of the technology.