Getting your thoughts written down helps you to organize them and frees your mind for new thoughts. Only un-developed ideas are hard to write down. Most ideas will remain un-developed until you try to write them down. Conversation is over rated as a tool for learning. The monologues of which it is composed may be great but synthesis usually requires time to think about the stuff said.
Plagiarism is a type of replication.
Even a book of recycled ideas, like a quote book, is valuable. Everything has been said before, the hard part is to find the good stuff. Most ideas are rearrangements and new comparisons of things you ve heard. Some thoughts are your own creation, but others have created it too. It is written out in some dusty volume.