When in reality change of characterization can be conditioned by various factors such as character development with some maturing and developing new traits and quirks because of that; or showing previous ones but in more grown up ight.
Some unexpected trauma or circumstances, various experiences, people protagonist in question met and inreracted or challenges it dealt with which left influence on fictional character psyche starting to harden up. Or do exact opposite closing in itself and becoming more quiet deviating from previous attitude he/she displayed.
In Jessie and James case its neither of those, but writers themselves being in highly delicate and in lot of ways ungrateful situation.
Which in my opinion is cause behind inconsistent portrayal of emotions and unique characteristics specific for Jessie and James personalities now in XY series.
Rocket trio and how fans perceive them caused always lot of polarizing opinions. Some absolutely adore goofy Jessie, James and Meowth coming up with jokes, silly tantrums and all kind of wiles they come up with . They do not mind Jessie and James chasing after Pikachu and being blasted of.
On other hand some prefered more whe Jessie and James were finally given more serious and important role to plasy in pokemon anime.
Resulting in more organized, serious and toned down in expressions, humor and moments of arguing/ talking about their ills .Due to having already limited time on disposal in Unova dedicated mainly to concentrate on fulfillment of missions. But also writers wanting to portray Jessie and James change in characterization as someone who out of gratitude and excitement of promotion given to them didnt wanted to disappoint and fail enthrusted confidence from their boss.
Hence acting more serious and fixared solely on tasks to better reflect vibe of TR trio deciding or at least trying to be more competent villains.
However this change wasnt accepted well among fans who preferred more comedic JJM trio and times when they displayed wide range of emotions and traits characteristic for them.
So as caught between two fires i imagine writers decided to play safe with portrayal of Jessie and James characterization in XY, Kalos series, By retaining some of that competence still holding higher rank among TR members and enjoying full thrust of Giovanni and TR admins, but also reviving on some of that silly, goofy side of theirs.
Does that meant Jessie, James and Meowth stopped having personalities in Kalos?
I wouldnt go that far.
Because there were quite a few, infact more than few moments where Meowth conniving, ambituous and scurvy personality came to expression. Jessie temper, dominance and proactive nature taking lead. In fact her vanity and selfcentered attitude was showed as well such as in wanting to film pokevision with her in starring role.
Or James submisive, insecure personality with tendency to become despondent when left on his own to make decisions.
Enjoying in Team Rocket presence in various episodes such as masking themselves in fake Ash, Serena and Bonnie deceiving officer Jenny and putting all blame on real group of cheating, stealing food and causing chaos in harassing peaceful life of its citizens.
Definitely one of most clever and ingenious plans they ever came up with in my opinion.
In using more effectively their pokemon like Inkay and Wobbuffet by resorting to ink sprays to blind opponents. Relying on calculated use of Wobbuffet counter and mirror coat to repell attacks from Ash Pikachu and other group pokemon giving them bad time. Even Jessie Pumpkaboo showed some half successful results in battle, more notably in Pangoro episode coming of as threat.
Jessie, James and Meowth being terrified to death by Espurr running mindlessly. Showing how they still have lot of emotions, irrational fears and life into them.
Being embarassed and ashamed at failed plan to catch Pikachu ending tricked by Malamar in taking control of them(except Meowth), with James collaborating with Ash to stop this pokemon reminding me of previous days. When Rocket trio and Ash with friends teamed up to get themselves out of trouble. Displaying again how TR arent unreasonable and corrupted to bone villains capable to feel sympathy and get over differences in aiding help to "enemy side" .
Even at Summer camp i liked how at times they seemed to forget about catching Pikachu enjoying to work at kitchen.
So i wouldn't say they are robots, "emotionless drones". Not at all.
But what Jessie and James especially lack now in Kalos aga are episodes which would focus more throughly on their interests, expressions, personal dreams and moments of disagreement and cooperation when being alone interacting between themselves.
What TR needs are episodes focusing on themselves exploring and reminding audience of their own individual virtues and negative sides. Such as James passion for bottle caps, naive attitude in falling down for other people schemes. Jessie vain, shallow aspect of personality caring more about exterior than inner beauty or crazy fantasies and insight in her past like we used to get in OS, AG and DP. Meowth contemplating about his role in TR and how to please Giovanni demonstrating his infatuating side.
Its not that Jessie, James and Meowth didn't showed to still have emotions, flaws, personal interests and personalities in XY.
It just happens those personalities currently portrayed, their own quirks and inner thoughts arent complete and more dimensional as of right now.
Due to limited screentime given in Kalos, in fact highly limited compared to previous series before BW. As well lack of episodes focusing on their own characters and daily lives when not preparing plans to steal pokemon and disrupt main cast journey.
In short Jessie and James as far as im concerned do have personality in XY, but that characterization due to scarse focus isn't fleshed out as much as it could be.
