I was happy to see them add this option when it was first announced because random teammates can make or break your game depending on who you get, so I'd rather just go in alone instead of pray to rngesus for a good squad some days. Plus, there were times I was getting put in alone or short handed anyway, so a no fill option to just save me from disappointment in the matchmaking system and my lack of a squad was also a reason why I was looking forward to it.
...I never expected it to break the game this badly though. Duos is just an absolute mess, and it's faster to queue solo in duos by not unchecking fill squad. 9 out of 10 games I play in duos mode are now solo with fill option on, despite the limit to number of solo players supposedly also implemented with the no fill update. Most games I see in duos are barely half full, and half of the teams are solo players themselves. Actually trying to go in no fill has, most of the time, resulted in a much longer queue time and, sometimes, the matchmaking just gives up and throws me in with someone on my squad...it's absolutely insane how much this broke duos.
Thankfully, trios isn't affected as much as duos, but I think it's only because most people aren't crazy enough to go in solo against full squads of 3 everywhere.
I guess I should just find some friends on here to make my experience more enjoyable, but as of right now, it's hell trying to play when you never know who or what you're going to get thanks to the matchmaking...