as for buying, things have been bad ONLY for those who bought bitcoin in the last week of the last month of 2017! otherwise for anybody who bought bitcoin before that, ~80% of last 2 years the price has been above their entry point...
This is not true, it may seem like it but the numbers have something different to tell us, there is no other way of defining "bad" , bad is bad and that's about it.
in the past 2 years, you only had 6 out of 24 months to go lump sum and still be in the green now which are November 2018 to April 2019, any other period and you would have been either in a loss or close to break-even (which can also be considered bad to many people)
So most people who bough bitcoin going all-in or lump sum are now in a negative territory, which is why cost averaging is a much better in terms of reducing risks, and that has been explained in the OP.
another point I want to add, that despite 2 years being long enough, it's not long enough to avoid the risk of bear markets, this is what history has proven, it could get worse depending on when will
BTC see a new ATH to make those who bough the last ATH in profit again, my guess is 3 years minimum, in case someone accidentally buys the top of the market.
edit:
or maybe this can be a little more accurate.
I hope we all agree that minimum time span fro long term hold is 4 years. Using that numbers will give magical results.