The lack of documentation is also a problem with specific projects only, not a widespread F/LOSS issue. And again, if the project lacks in this area, you have the means to improve it.
As for projects being difficult for newcomers; yes, this is an issue. But it's one you'll also encounter when approaching _any_ codebase, where you'll find it takes time and effort to understand and contribute a meaningful change. If you're not a programmer experienced in a particular tech stack, then it's obvious the barrier to entry will be even higher.
None of these issues are specific to F/LOSS, so the post reads like a rant from an entitled user. The right mindset to begin with should be one of gratitude that developers are granting you these freedoms which you don't get with the majority of consumer software nowadays.
And another benefit of F/LOSS: just because a project is inaccessible to person A, person B might find it easy to contribute, which encourages a community to exist, from which everyone ultimately benefits.