This is the best call and all your words are most powerfull. Yes, we should advice all to invest in BTC and stay satisfied with it. As we can know from the previous history , all altcoins dump when btc is starting to make a rally or make a little dump. So, altcoins are nothing but just a exchanging things in exchanges and worthless without any exchange. But some of the altcoins have uniqueness and they do good in every markets. So, everyone can also take a look into those. 
Not on bitcoin is the coin to invest on, ether, litecoin and EOS are all good coin someone can invest on too, but for people that do not know about crypto investment and trading, bitcoin is a good choice for such people, but investing in some altcoins are protitable for good traders, you can see any good traders trading only bitcoin, that is not possible. But, it is easy to learn and less risky to invest in bitcoin than altcoin but not that altcoin can not be professionally as well.