It seems to me that you have a common misconception about the nature of scientific publications. You talk about somebody wanting to "present a paper" and "an interesting idea," but you do not mention what this is intended to accomplish. This sounds to me like you're thinking about the publication as an end in and of itself, or as a way of making scientists listen to your ideas. Neither of these is the case.
Scientific publications are, ultimately, about communication. They are part of a long, slow dialogue within a community, and peer-review is a filtering process by which a sub-community attempts to determine "Is this piece of work substantial enough to consider taking seriously?"
If you just want to get your ideas out there, you don't need peer reviewed publication. You can disseminate ideas through many different types of media, and if your writing is well-presented and interesting enough to others, you can draw attention and affect the scientific world without any need for peer review or even credibility (more's the pity).
If, on the other hand, you want to make scientists listen to your ideas, peer reviewed publication won't do that either. Most scientific publications are barely read and never cited. To have an impact on scientists, you need to figure out how to speak their language and how to participate in the community and its conversation in a way that relates to what other scientists are thinking about.
Honestly, this is really hard. It's not because science is closed and wants to keep outsiders away: some sub-communities certainly hold such attitudes, but usually there are other related communities that are quite open and welcoming of newcomers. Mostly, though, it's hard because you have to prove that, out of all the vast number of ideas floating by every day, your ideas are the ones that are worth the time and energy to consider carefully. Doing that requires gathering strong and objective evidence, presenting that evidence in a clear and compelling manner, and placing it in the context of the larger dialogue in the community with which are you attempting to communicate. All of those are difficult, and if a paper fails on any of them, it is likely to be rejected and/or ignored, because the people reading it won't understand why it's worth paying attention to.
Now, what does exacerbate the difficulty of getting involved in science is the difficulty of getting at some sections of the literature. High-cost subscription-only journals can make it impossible for outsiders to access key parts of the ongoing conversation, thus making it much more difficult for them to participate. Some parts of the scientific community have taken good steps towards addressing that (e.g., physics and math), while others are generally quite terrible. If you're dealing with one of the latter, then many scientists will still gladly share pre-print copies of their articles, but it does make things much harder.
