Wouldn't they have something more to say to people than, "just buy BTC?". What would they tell people should be the criteria for their investments? What coins do you think these early crypto investors are investing in currently as a compliment to BTC & ETH, that they believe will help newer investors meet their present day goals?
Well the question is related to BTC, such as "Should they buy BTC" after all, so I reckon the answer of just buy it is actually more than enough of an answer. After all, considering the positions of early investors, I don't think they've made a loss if they've continued hodling till now. Criteria for choosing another "Bitcoin" though? Kinda hard to give since it's been a decade and Bitcoin's still the king. The rest of the coins that were released are either shitcoins, or Bitcoin but with caveats (as well as its own advantages, but caveats still are above it imo). If it was just choosing another coin, well that depends now on how well us as investors can actually understand what they want to do and what their plans are.
I believe helping new investors achieve what they want is close to nill, at least in the short term. A lot of money is lost in the process of learning to invest, and I highly doubt they'd stay after losing a few thousands of bucks. If they stay though, that just means they're prepared to lose more, not necessarily achieving their goals immediately.