Rogue's powers wax and wane, as she has gone through several powersets. I wouldn't consider it a straight power-up, as some of her longest eras were when she was arguably weaker such as with Carey. As far as Gambit goes, he's remained more static. IMO it's less a regression, than writers just not being creative with his powers. He can still show off a ton of versatility but a lot of times people don't think outside the box with his abilities.
While Scott's optic blasts may be allowed to hurt "more", I would argue Remy should be able to handle himself a lot better in close quarters compared to Scott with his H2H experience, bo-staff and enhanced agility.
Right, I think KTs Rogue was powerful but wasn't as OP as people think. She did get knocked out or injured fairly frequently in Mr and Mrs X. Because of how short the run was, KT also didn't get show off Gambit as much either I think, since the story KT focused on were Rogue-cenetered. Gambit should be able to keep up with Rogue in terms of enemies, given the right tools and intuitiveness.
Let him use his charged bo-staff as a conduit more to hit-hard and make him more of a threat in close-quarters. His staff can be strong enough to deter metahumans as strong as Rogue.
As well as allow him to delay explosions to use in more situations and show off his intelligence.
Heck maybe also allow Remy to access tuned down versions of New Suns abilities like slowing down the kinetic potential of an object or simulating stopping time since he did get resurrected post-Otherworld and might not have the inhibitors Sinister had originally placed anymore.
Writing Gambit as a one-trick pony who just throws playing cards is not using him to his full potential at all and why I think the gap seems as large as it is, when it shouldn't be.