I don't think that this is a good idea. Some people join this place because they have a couple of questions, or they need help with their game. While removing the New Topic button for new members would greatly reduce the amount of spam topics, topics that are in the wrong place, etc. it discourages them to join the forums in the first place.
If a topic has been posted in the wrong place, report it and state that it needs to be moved, and possibly where it should be moved to. If someone starts a spam topic, report it and state why you think it should be locked or binned. And, if someone starts a new thread about a subject that has been covered recently, report it and add a link to a recent thread on the subject to the report so that things can be dealt with quicker. There is an adequate amount of forum leaders and moderators that do their best to keep the forums clean. And you can help.