We love BB-8, but it seems like Rian Johnson really struggled to find things for the quirky little droid to do in The Last Jedi. While much of BB-8's plot works, there were definitely some shoehorned contrivances and missed opportunities along the way. Instead of teaming up with a stranger like D.J., it would have made more sense for the loyal and skittish droid to stay close to Finn and Rose at the casino. This would present some problems during their space-horse escape, but that's part of the fun. Another high point was seeing BB-8 masquerading as a MSE "Mouse" droid—complete with mimicked beeps. However, we really were hoping for more interaction between BB-8 and its First Order counterpart, BB-9E.
Finally, BB-8's "coin gun" was a harmless and fun addition to the movie, but Johnson went too far by having the astromech droid kill First Order soldiers. BB-8 is programmed for repair and flight navigation, not battle. In BB-8's comic book appearances, the droid has never killed anyone and occasionally uses only non-lethal force to help Poe. Even if you accept that this ball-shaped droid could actually climb into an AT-ST, watching cute little BB-8 actually kill people was shocking. Instead, we wish D.J. had gotten another scene after getting his money, where the anarchist surreptitiously catches BB-8's attention and nods towards the walkers. This would set the stage for BB-8 to create a diversion for Rose and Finn's escape—but one that doesn't involve murdering anybody.