I think that's exactly it.
I never understood the positive response some people had for the movie - it seemed to be a heartless tale about terrible people, and not a particularly interesting story either. And yes "boorishly stylish" is a great way to put it!
(The "on reflection, this was pretty mediocre" thing occasionally happens with videogames as well, I note - sometimes a game is very well-reviewed on release, and then a couple of years later, people are like "Why was this so-so game getting 9.5/10 reviews?!". It was particularly prevalent from like 2000 to 2015-ish, but is less common now.)
Whereas Goodfellas is incredibly charming, and that's why it works. De Niro or Pacino couldn't have pulled off what Ray Liotta did in that role.