The development of alternative cryptocurrencies, also known as altcoins, had both positive and negative impacts on the early adoption and growth of Bitcoin.
On the positive side, the emergence of alternative cryptocurrencies helped to increase overall public interest in the concept of cryptocurrency and blockchain technology. By offering alternative options to Bitcoin, altcoins helped to broaden the appeal of the cryptocurrency space and attract new users who may not have been interested in Bitcoin specifically.
No, I completely disagree with your opinion, altcoin have not done nothing to bitcoin which you think can hold bitcoin adoption.
Altcoin helps bitcoin to gain more authority, some people learned about cryptocurrency by getting into altcoin investment first.
Back then, if I can remember correctly you only can buy bitcoin from an exchange then convert or trade them with the altcoin you want to invest. So altcoin did boost the adoption of bitcoin. So I don't see a single negative site of altcoin here, or at least altcoins did nothing wrong with bitcoin.