Ridiculous that Ghost Recon does this but R6 Siege can't. The fuck is going on at Ubisoft?
TL;DR:
Ubisoft Montreal has serious issues, Snowdrop (The Division's engine) took years longer than expected/planned, and Ubisoft has a finite--not that it ever seems that way--number of studios.
Storytime:
Once upon a time Rainbow 6: Patriots was under development by Red Storm, Ubisoft Montreal, and Ubisoft Toronto. This was cancelled. Ubisoft Montreal, being not the best at doing anything but tons of same-y content, then stole Red Storm (speculation; I have no inside knowledge) and stuck them on Far Cry 3 & 4 instead of either Rainbow 6: Siege or Ghost Recon: Wildlands which would be the natural/obvious plan. This would be a major reason Wildlands is taking so long, since Red Storm historically partnered with Ubisoft Paris on Ghost Recon, and it would also be a major reason Rainbow 6: Siege is coming out the way it is since--as above--Ubisoft Montreal has serious problems on everything except hitting release dates (one reason I was shocked Watch_Dogs was delayed).
Around the same time Ubisoft Massive begins running into delays on Snowdrop, and (fall 2013) asks for help though their PR phrases it as looking for partner studios that fit with them blah blah blah: let's be clear, they were in trouble. The engine began development as a clean slate next-gen engine somewhere in 2008, by Massive pre-Ubisoft acquisition. I speculate part of Ubisoft picking them up was that Ubisoft was thinking the same thing as EA with Frostbite, one engine to rule them all instead of Ubisoft's Montreal triple engine mess. Sadly the engine clearly ran late (rumours were that the engine wasn't done until late 2014) and so Ubisoft began throwing studios at The Division. At this point we now know the following about Ubisoft: Paris is doing a good job on Wildlands, though it took a while, since they have no backup studios; Rainbow 6: Siege is Montreal's baby / they think it is fine / Montreal is bad at game development as usual; The Division is in need of serious help, but it seems to be primarily a content thing because Snowdrop took so long.
(Below specific dates are when Ubisoft released PR on the subject)
- Fall 2013: As revealed when Reflections is added, Ubisoft Massive begins asking for help (they phrase it as finding the right partner studios, of course).
- 7 February 2014: 1 of the 5 Ubisoft Reflections teams, the big 40% of their 200 person staff team, joins The Division
- 9 April 2014: Red Storm Entertainment joins The Division.
- 11 May 2015: Ubisoft Annecy joins The Division.
I think The Division will turn out great, myself, and I also think Ghost Recon: Wildlands will turn out great. But Ubisoft Montreal churns out mediocre stuff constantly, so without Red Storm on Rainbow 6 I'm not even remotely surprised how weird/meh that game is turning out.