I also don't deny bitcoin is the best but that doesn't mean I will ignore the bigger opportunities with altcoins. I think we should not be too stubborn and ignore the opportunities to gain huge profits from altcoins, which bitcoin cannot bring us.
It is not a must to have only Bitcoin for our investment. It is no problem to have altcoins as well. Altcoins also have good potential to earn huge profits. However, we must be aware that altcoins are riskier than Bitcoin. If we choose the wrong altcoins, they may become dead coins and have no values in the next few years. This will never happen with Bitcoin, it must always survive as the number 1 coin in crypto space. So, we must be more careful to choose altcoins for our investment.Remember that it is not only about the chance of huge profits, but altcoins also may bring huge losses, too. We don't view the altcoins from the good side only, we must learn the bad side as well. Since altcoins have bigger volatility, the prices may be decreasing worse than Bitcoin. Make sure we don't choose shit altcoins, memecoins, or random altcoins with weak fundamentals.
People who are stubborn and try to impose their thoughts on others should not invest in altcoins, which reminds me of what gold investors also told early bitcoin investors. But as a result, because of their stubbornness, they missed the opportunity to own bitcoin when it was priced below $1k, $100 or $1.
Don't blame people who want to invest in Bitcoin only! It is an individual right. 
People who didn't invest in altcoins may not get the huge profits, but they also don't lose money.
It is just optional to choose altcoins, it is not a must! Just don't make it be complicated, mate.
You should know that not everyone that prefers to invest in altcoins due to the risk that is involved in altcoin investment, let me use myself as example. I'm not a lover of altcoinsm I prefer to hold bitcoin for long term investment I don't care how much profit they get from altcoin investment, I think is all about choice you don't have to decide for anybody if you think investing in altcoin is good for you then you're free to invest in altcoins, for me I have chosen to hold only bitcoin, I can't leave bitcoin for any other coin either.