Add .dropboxignore directory to exclude folders without using selective sync

I think everything we do is probably very similar, we work on files on a computer and often not in the same location as our colleagues. We don’t want Dropbox syncing certain files within a certain folder for whatever reason. Its not hard, and from reading this thread i doubt any of you have tried this at all yet your saying it doesn’t work. Emma summed it up beautifully, what would a .Dropbox placeholder do that the don’t sync feature doesn’t?  Or another way to put it, what other cloud based solutions of this dollar level do what you’re asking? I don’t reckon any of them come close. Google kind of has something but it’s a mess. 
I got it working with a placeholder as the trigger anyway, if I tidied it up and triple checked everything would you use it cause that would be a little bit of work, not heaps but ya know