A huge majority of cryptocurrencies are scams, but not all are scams. A cryptocurrency dropping in price(or going to zero) doesn't automatically mean it's a scam — it can also mean that it simply just failed. Just like how a lot of businesses, companies, and projects(startups) can fail.
Agree. Although there are many scam crypto coins, it doesn't mean only Bitcoin is trustable while others are possibly scams. Top altcoins such as ETH, BNB, ADA, MATIC, or SOL isn't scam coin. They showed proof that they can be trusted because they have clear and strong fundamentals. It makes them survive as top coins so far. Even if they may drop their prices drastically someday and be announced as a failed project, doesn't mean they are made as scam coins. You are right, every project has a chance to fail, it is something unavoided. Those people who call scams in each failed coin, just don't understand the difference between "scam" and "failure".
Among the currently trusted coins in the crypto world are BTC, ETH, BNB, SOL, MATIC, ADA, XRP, LINK, DOR and more etc. But there are some coins which are not at all reliable to invest and can become scam anytime. So to invest he must have an idea about kypto coins. If not, you must face losses in the future. So if you invest on the good coins before investing, there is no possibility of these tokens being scammed in the future.