What if I got an idea that has been recently published, should I invest time considering it?
Assuming that you want to work in this small sub area, you can pursue it. You are a bit behind the frontier if work was published a few years ago and you need to get up to that frontier if you want to advance it. That will take some effort and such efforts are worth it, just to develop your mind. 

But you also have new information that will help you get to the frontier quickly: the new paper and other recent work. 

On the other hand, leaving everything else aside to pursue ground that you know others are already plowing, seems sub-optimal. I'd suggest pursuit, but not that exclusively. Develop a lot of ideas shallowly (and keep notes) so that you can pursue a few of them deeply.