I somewhat agree with what you've said. Bitcoin is the only "reliable" coin that you can hold for the long term. However, it doesn't mean that people should stop investing in other projects. A diverse portfolio is always better than hedging your bets on just one coin or asset. I also see potential in SOL, ETH, and other altcoins. Of course, research is crucial and you must not invest blindly.
I remember my younger days here in Bitcointalk and of course in Bitcoin itself that people keeps
talking about Holding and keeping bitcoin alone things that I manage to follow also back in the days
but ending me regretting because there are so much increase happens in altcoins that I missed holding
nothing but just bitcoin so now I learn my lessons and like yours? diversified folio is what I keep doing now