No version of Lightroom has tools to find or remove duplicates, and the import dialog has the same feature that is supposed to prevent duplicates from being imported. Lightroom considers a photo to be a duplicate if it has the same file name, capture date/time and file size.
So upgrading Lightroom does not help in this task.
However, you might want to see if this plug-in works for you (note: I have not tried it)
My needs are that of an amateur photographer who doesn't need much technical stuff (e.g. i have no idea of the ISO or the lens type of any of my photos, and am unlikely to start following that information later). I do need organizational help and I love the ability to develop quickly. But I've been constantly vexed by trying to get all the photos in the right place. An "expert" I hired to help me set up on LR recommended having different catalogues for different projects. Later, the entire Interweb pretty much shook its collective LR finger at me for having multiple cats, and so I made one big master catalogue. And since then, things have been pretty screwed up. I'm not sure whether I should bother to upgrade, or simply leave LR and try my luck at something else.
Trying your luck at something else ... in my opinion, if you are not organized using Lightroom, then simply moving to different software does not improve your organization. And there really isn't any "luck" involved. Improving your organization involves YOU putting in the work to become organized. The software is merely the tool that you use. And so any photographic management software will give you tools to improve your organization. It's really up to you, the software is not the problem.