Pure BJJ is more about patience, and waiting for mistakes to happen. Most people now are cross training wrestling, sambo, judo, submission wrestling, etc so grappling overall is different. It's become more explosive, with scrambling, faster transitions, and explosive submission attempts. Like you'll see more people jumping on to the back and getting the hooks in while in the air during transitions currently than you would back then. That's some of the examples of the speed of grappling and explosiveness being added to it. Before it would go in steps in order to take the back and get your hooks in. Now steps are being skipped and they will just jump on the back during scrambles and transitions. There are a lot of other examples, but that's one of the easiest ones to point out.
Drawbacks probably would just be rushing into submissions and you may not always get it and could leave you in an un-advantageous position, but that's also where the scrambling also comes in to play. I think it strengthens grappling overall. Since the slower paced grapplers would get out scrambled before and now they're working on scrambling as well as their techniques and submissions. This is why pure bjj has had problems with wrestlers in the past.