that's what it is there for though - if you're hit with a manual penalty and need to show google that you're making a valid effort to clean up your mistakes (a last resort effort).
it doesn't do anything when you don't follow the guidelines for submitting a request, or submit a request without showing that you've attempted to fix anything first (ie removed the links manually, contacted the webmasters of each site up to 3 times, etc)
lots say that it CAN be used to prune/clean your backlink profile in order to prevent penalties (many believe that the disavow tool essentially nofollows links that you submit to it), and this is where most people probably think it's not working. you usually won't get a response from google when submitting a request, and it can take months to process.
all in all, it does work, mainly when you need to submit a reconsideration request and have someone manually review your site for reinclusion in search.
the main thing OP really should ask himself is doing all this cleaning/rebuilding really worth the time and effort, or is just starting more new sites a better use of time. you can rebound from algo/manual penalties, but it is slow and painful and it takes a ton of time
, and + you really need to have a good idea where you fucked up in order to not make things worse/harder on yourself