I actually had my first rage quit due to this recently.
I was a squishy rath but knew we lost center, so I used the shards I was saving for my gear to build the shock turret up to tier two and force the team out the center, and would’ve worked. I go for the assassination on their support alani, (she was at 10%) and got focused on and died. When I watched the kill cam and map I realized my team did not move an inch from behind their safe haven sentry and push them back EXCEPT FOR MY ALANI who saw what I was trying to do and tried to offer assistance. It happened three times to the point that I just quit the game and got off Battleborn.
I recently have been seeing an increase with this in PUG. It’s like the players want to stay alive long enough to lose. They don’t try to push for shard control, they don’t try to take out shock turrets to try and get it up for use to take control of center, they just safely stay behind the turret, living long enough to just surrender. And like you said, this is level 100’s that’s doing this.