Bnb is good it is also very useful coin, but investing on bnb alone can make you bored, i think investing on some new fast moving coin and btc is more great than investing only on bnb, i believe that if we invest on different coin there is also a different excitement when we look or check the price on our portfolio.
if we only bought bnb coins, we will lost opportunity from another coins which same potency with bnb too. for long term bnb proven as good blockchain and alot projects join in its ecosystem.maybe another layer 1 project could added to our bag in order to compare which chain is the best.