I strongly believe that there are altcoins that ofc are scams. The key here is to never invest in something that acutally doesnt offer any value or wont produce anything. But to say that all altcoins are scams is a faulty statement.
A good video where you address the issue and give reasonable answersLike @leftbank said in the comment section, "investing in cryptocurrency is similar to investing in other assets and diversification is critical".