Everyone who would read this forum and post in it will share your concerns. There are, however, too many parents and leaders who view the MB as a piece of cloth rather than an achievement.
The Guide to Advancement addresses group instruction and states that it should only be used when there is a valid reason or benefit. An example might be that there is only one Oceanography MBC, and his time is limited. Another might be that the local Ham Radio club wants to have a clinic and bring the necessary equipment to a Scout Hut for the day.
I do Bird Study at a MB day (two, actually), but several of the requirements must be completed as prerequisites, and the boys must meet me the next day at a local birding venue to complete the field work. I'm flexible if another badge has a follow-up at the same time, but sadly, most don't.
I will say that my district is strict about prerequisites. If you don't bring them you can't earn the badge, even if there's no follow-up work.
I share your lament about missing out on adult interaction. It's one of the methods of Scouting, and there's no substitute for it. At Eagle BORs you can tell which boys took the initiative and called the counselors and which ones showed up on MB day.