I agree one need to take the responsibility to their purchases.
That being said, personally I think it is better to buy coins at different times, the price differs but the average price is relatively good then as opposed to the strategy to invest a big chunk of btc at one shot and then pray your timing was good.
Experience plays a part, too. If you've been in the market for a few years you can see a bottom. I've been playing the market for three years. The summer bottom in bitcoin was apparent. I bought, and though I made some subsequent trades that were maybe a little ill advised, I'm still well ahead. Similar experience with Monero. I've learned that about myself: fairly good at seeing buying opportunities, not so good at knowing what to do thereafter.
Moral of the story: it's not just the market you have to learn about; you must also know yourself.
If you are inexperienced, dollar cost averaging is kind of a default strategy.
