To chime in as a lesbian, tribadism is definitely a thing in lesbian sex (maybe not the most used) but there seems to be a lot of misinformation and therefore heated debates on it because of that, especially due to lesbian porn catered towards straight men.
So here's my take: tribbing exists, it is used and can feel good but people often forget or do not know it can involve more positions than just scissoring which seems to be the most hated yet most seen position in porn. In the end it's simply the act of grinding your pussies together or even on another body part and can be done in missionary position, sideways (or any position the couple figures fits best to them) or even with a bit of help from a toy and leverage with a pillow. Personally I love depictions of tribadism cause I find the act of stimulating your pussies through grinding them together very hot if it's done right and I wish it was taught more in lesbian spaces instead of demonized.