I feel like most of what I do in judo doesn't improve my BJJ at all.
I feel like this is a personal problem of yours, and i also feel like you demonstrably lack the proficiency to make this statement.
-------
Progress will be slow, but any Judo is better than no Judo. as stated, some moves need to be modified to BJJ context otherwise they're basically a flying back take.
Judo is way, way the fuck more high-impact than BJJ. It's basically the art of flinging yourself and other people at the ground as hard as you possibly can. You can mitigate a lot of that impact with proper training, but again that'll take you a longer time to develop good falling and acclimate to repeated impact.
as far as the rules, it'll depend on who you learn from. i don't see the point in not teaching the leg grabs unless someone has olympic aspirations, which is a long, long fucking shot in America. being the best Judoka in America is like being the best baseball player in Japan - you might be able to hang in the big leagues, but you're not exposed to anywhere near the same caliber of play.
taking out leg grabs took away a lot of intuitive grappling reactions to positions and (i think unfairly) favored one style of play over another (read: was designed to impede the dominance of mongolian and eastern european wrestlers.)
that said, cross-training is a good thing. BJJ and Judo are very complimentary to one another, like two wings of the same bird. training both helps you close the gaps in your game.