How much have you really invested in bitcoin or altcoin? i think the OP is making sense, do you buy ETH at 1,300$ per one in early 2018? what advice do you have for such people? to sell and use the money to buy bitcoin? or hold on to the tokens and wait for market recovery? sorry your strategy is b********
For those who bought in at highs, not just for ETH, but many other coins, the best strategy probably would be to get the buy-in price lower by buying up coins at a cheaper price while they can. Of course that is only a viable strategy if you believe said coin will appreciate in the future and it actually works out that way. It also requires additional funds and additional risk.... but it's one of the few ways to dig yourself out of a humongous loss.
Simply taking a loss and moving everything to btc is an okay strategy when at a minor loss or if you feel whatever coin you invested in is utterly doomed. I wouldn't put ETH into that category however... but if someone for some odd reason decided to put their life savings into Dentacoin (or whatever junkcoins), they might want to look at an exit strategy vs buying up more dental coins.
I do agree with the OP that holding is probably the best strategy so long as we aren't talking about requiring a miracle to recover losses -- so those who bought their alts high, but not at ATHs -- may be better off simply holding unless they spot a better opportunity.