Of course. But this isn't a question about what is or isn't in the documentation. Of course everything you need to know should be in the documentation, and you should RTFM.
No, it's about obfuscation vs clarity, and to an extent, about how good the overall design really is. Look at it as a measure of quality. If I have to read every word of the documentation to find the tiny part on page 18 where it tells about that one flag I need to start it up with in order to ensure that one feature works the way I want; versus a sensible default and clear documentation and even clear design where perhaps that flag isn't even required (think automated memory management that Just Works, versus a dozen command-line or config-file switches about memory buffer size and such).
When you run into issues, it's not a useful excuse to say "Well, you should have read the documentation, it was all there." That's like a shady credit card contract where the rate goes up 30% if you miss a payment. It's easy, even if you read it, to say "well I won't ever miss a payment," and even easier to miss that clause completely. Can you blame people for not reading the fine print? Sure, it was their responsibility. Will people still do it? Of course. Will people who read the contract fully still run into issues if they make one mistake? Probably.
And the point: is it a crappy contract? Yes. It has a crappy feature to begin with, and it's made worse by its obfuscation. This is almost unarguable: a credit card with a lower rate penalty is better. A piece of software with good defaults and sensible design is better.
The requirement for asinine and lengthy documentation isn't just a big warning sign that you should read it—it's a sign of poor design, or at least the word everyone's been using to describe Mongo: immature.
Good design includes the whole experience of using the software, and takes into account good integrated systems and human interaction. Bad design requires you to read the documentation extremely carefully. These are not hard and fast rules, but they're certainly warning signs. Really clear and obvious warning signs. And the overall point is that the well-documented issues that come up with Mongo are not just stupid people who don't read documentation—they are statistically relevant pieces of evidence pointing to some poor design decisions.
You should really think of this whenever you see a trend. You have a choice. You can blame individuals for "not reading the documentation"—or you can look at the systematic trend and statistically evaluate the problem. The former allows you to quickly dismiss issues on an emotional basis and make yourself feel better, while doing absolutely nothing to solve the issue. The latter lets you collect useful information and make real changes that have a real impact on the issue at hand. Your call.