The veteran neo-soul singer issued a scathing rebuke of the 2 artists' live-show choices -- namely, their tendency to bare their bodies onstage ... which was again on display this past weekend during Essence Festival, where both MTS and JM grabbed the mic.

Their respective sets went viral ... in Janelle's case, it was because she ended up flashing the audience -- revealing her right breast (which had a nipple pasty). She's had a habit lately of dropping her top, but has said she feels comfortable in her own skin.

As for Meg, she didn't really do anything too crazy ... just a little twerking of her booty, which she always incorporates into her routines, and for which she's kinda become famous.

In any case, India wasn't feeling the perceived peep show they put on, and she sounded off about it on IG, saying ... "The issue is what is CONTEXT. Humanity does EVERYTHING. But does EVERYTHING BELONG IN A STAGE. No. is everything for KIDS? No."

She continues, "So when we as a culture make something like this mainstream -- it shows a lack of discretion and discernment. To those in the comments who laugh at anyone who wants these things for our culture, you certainly have that right."

India adds this though ... "Just as many folks have the right to want our MAINSTREAM International export -- our Music -- to show us in a respectful light. I'd like to on the record saying: this wont age well and that's my issue." She finishes by saying she loves Janelle and Meg, but just not how they're choosing to express themselves in this regard.

Her critique, although somewhat apologetic, is getting roasted by fans dropping memes and GIFs mocking India.

Essentially, she's getting branded a prude and an old head, who should keep her comments to herself ... and let the younguns live!