Personally, I continue to hold altcoins. Someday their time will come when the domination of Bitcoin will decline. Maybe it will come in the fall, we'll see.
Certain logic, of course, is in your words, but these are only your judgments, because there may be such an option that Bitcoin will become the number one coin and the Altcoins will become a thing of the past. Although up to this point I still think the Altcoins will have a wave of growth.