Baron plays require deep wards to spot the enemy coming, it requires your jungler to have smite, it requires their jungler to be dead, it requires your team to know they need to peel off the Baron when it gets low and zone the enemy away from the steal. It requires a tank, and it requires some good objective DPS on your team and present.
The potential for any of that to go wrong in solo Q is massive. Many junglers, and most non-junglers, don't know how to set up an objective play properly.
Also, it's really, really important for your team to realize it's actually easier for the aggressing (stealing) jungler to land a smite, than it is for the defending jungler. If you are taking Baron, and you have Quinn/Draven on your team, and they start trying to burst down the baron when it's low HP trying to help you secure - they are actually making the HP drop as erratically as possible - this makes it harder for their jungler to secure the smite. It also makes it easier for the enemy (stealing) jungler to land their smite. The best thing for your team to do when taking Baron is NOT to try to burst it down when it's low, it's to zone the enemy team off and let the jungler land the objective solo, smoothly: smooth is better than fast (erratic).