Everyone doesn't know LUNA holder's investment will be zero, I suggest always don't invest your investment in one altcoin always invest in different altcoins, you can invest in BTC because all market depends on BTC and BTC never can be zero and we can believe that about other altcoins so invest in BTC is a good idea.
I believe that BTC and ETH are blue chip projects that will never be zero, no matter what happens they will always be at a high level and I doubt it would ever change.
So, I agree with you that we should do our investment towards them, but at the same time they are just profitable "enough", why not change it a bit and have 3-4 good coins that covers 90% of your portfolio and then you could end up with something that would be a major big earner if you are lucky, if not then you could cover the loss from the other blue-chip projects that you invested. It is not smart to risk it all, but it is not smart to never take a risk on anything neither.