It's not their fault, yeah, but when you are a maximalist, you can miss out other opportunities that could have earned you thousands or millionaire of dollars. There are lots of scams with the altcoin market but there are also some opportunities with a few tokens, but if you are not ready to risk it, better you only accumulate Bitcoin.
The challenge is how will you be able to identify projects that are genuine in the altcoin market. Some of them that have failed looked promising but the majority of them end up becoming worthless, and just a few become profitable. Some people don't like these altcoin's complexities, so they decide to focus only on Bitcoin. Don't just look at only the money people have made investing in altcoins, others have lost fortunes because they put their money in some of these failed projects. Just as you said, if you are not willing to take the risk associated with altcoin, Bitcoin is the easiest and safest crypto investment.