However, what makes a lot of sense (and I've seen a lot of bitcoin Maximalists do) is to recommend keeping a bitcoin portfolio alongside an altcoin one but Bitcoin has to be the #1 asset and have the most weight.
This is a simple and highly effective strategy, with this strategy we will be safe because the majority of assets are bitcoins and we also have the opportunity to get bigger profits from small investments in altcoins.
Holding 100% bitcoin is not necessarily a bad idea but it is not perfect either because we will miss out on many great profit opportunities from altcoins. Many people are too conservative and stubborn when they don't want to invest in altcoins but they also try to prevent others from investing in altcoins. That not only makes them but also makes others lose out on greater opportunities. They forget that we are here to make profit, not to prove right or wrong.