Poirier is still easily top 4 or 5 of his division. He should absolutely quit should he desire, he's been doing it forever, but he's still at the top of the game right now, at least for another year or two.
This is just two of the best guys in the division doing what they always do and have done in the past.
Like Gaethje said, sometimes luck and chance is a factor and it could have easily just gone the other way. Their first fights is one of my favorite of all time and it really made me a huge fan of Poirier.