Not instead but with Bitcoin. Do not go all in on altcoins as you should not also go all in on Bitcoin. This is the best option for me. This is diversification, not putting all your eggs in one basket. Whatever happens to either of the baskets, there is still the other.
Diversification is used when you don't know what you have invested. Instead if diversification, you can maximize the profit by invested more in coin which you think is interesting and promising. Why we need to diversify our money to many altcoins with low amount instead focusing in few altcoin but with higher investment?
Diversification is the best option in terms of crypto, stocks, and other investments. It is not an option for those who are ignorant on what they are getting into. Diversification is encouraged by I would say all veteran investors. I am quite surprised when you claim diversification is only used when you don't know what you are investing into.
Investing on a single coin, stock, currency, or anything which you think is interesting and promising does not make things better. That is risking everything in a single shot.