You know the factors to consider when investing in bitcoin**, and those kinds of considerations could be accounted for when considering shitcoins or various other projects as well.. including ICOs, Defi, NFTs... and then sometimes if we are considering diversification, there is a difference between diversifying into different asset classes versus diversifying within the same asset class (if you might know the difference or that something in the asset class is sufficiently different or even worth investing into).
Diversification of investment assets may be a good option to pursue so that one can profit from several other assets besides just bitcoin. But I think right now it will be better when they focus more on bitcoin investing rather than diversifying assets into altcoin because the current bitcoin price has given them the opportunity to get it low price.
I wouldn't recommend an ICO, Defi or anything like that for anyone at this point other than just bitcoin. If they don't invest at this point where bitcoin has lost 75% of its value since ATH, then I don't know of another best time to do so. They can still invest in altcoin at any time, but it would be better if they don't miss out on investing in bitcoin as their main investment now.