Only a few altcoins have the potential other than Bitcoin. So yes, not all the posts you have read are completely wrong. Just spend some time to research and you will see.
Yes, because everyone has their own thoughts in making posts, so we also can't immediately believe the posts they make, so I totally agree that someone should take the time to research the truth of the potential of all Altcoins apart from Bitcoin.
That's always the way investors do it! Investing in something is not simply looking at other words and follow them. Of course, each person will have each different judgment about a particular project, some believe some don't. Therefore, those posts like this is a good way for us to know which coins to consider. Though, we still have to do our own researches to decide which coins to invest.