I understand, and you're not alone. Many are cautious of altcoins. However, not all altcoins are scams. Ethereum and Ripple provide new technology and ideals to crypto. I agree about the sentiment-driven market; Bitcoin is everyone's big brother. Everyone moves when it does. But why? Is it sentiment or more?
Imagine if every coin had sentiments. Would the market be stable or chaotic? Bitcoin is powerful while being decentralized. I advise you to diversify, investigate, and never put all your eggs in one basket, even if its flashy and called Bitcoin.
I've got the idea what you were talking about, but I like to stay on the safe side. That is the reason why I always choose Bitcoin. This is not something that I don't diversify my investment. I do it within the Bitcoin investment. The simple solution is DCA. To me, I call it diversification of my investment. I don't have any problem with other coins but just to be on the safe side I invest only on Bitcoin. Other people have other kind of opinion about this. That is the reason the market is still moving because there are people trading other coins. That's not my problem, they can do whatever they want. This is just my personal choice.
And I don't think it is totally based on sentiments. Some of the old coins that has been around for a while will most likely follow the trend of Bitcoin. It's not you and me, it's the people who connect the dot to create the sentiment. Most of the new coins or maybe some of the old coin could potentially move based on hype and trend. There could be sentiments involve in it, but it is most likely hype and trend.
So yes it is not always sentiments, but if you want to look at the major coins' movement they are most likely happening because of sentiments attached to Bitcoin. And yes Bitcoin is not the only investment that I do, I have other businesses too.