I don't see any reason MS shouldn't be pursuing GAAS for their 1st party. The single player focused titles they have attempted this gen failed, and while units are down on titles like Halo and Gears we don't know how far down actual revenue streams are due to increased digital spend.
Despite what GAF and other forums think about the idea of GAAS they are what the larger broader demo enjoy. After all a game like GR Wildlands which was lambasted largely by forums and wasn't super well reviewed by enthusiast press is the best selling title of 2017
But that's the thing Ghost recon, Rainbow six are co-op/multiplayer games always have been minus first couple rainbow six games.
Those are games that you can continually ad stuff too because the majority of it is online. Halo, gears, forza are games that are mainly campaign/career/ story driven with co-op aspects and multiplayer. They have now shifted to where the majority of focus is online and such MS has implemented with req packs, and the card packs/crates in gears.
Then to add salt you turn a franchise known for it's amazing single player campaign like Fable and turn it into a moba/f2p style game that didn't even know what kind of payscale they wanted.
It isn't working, and not putting faith into possible great IP's for the long run doesn't help either. Cutting and running on their single player efforts doesn't do them any good. Now they are currating games based on XBox live activity and multiplayer trends when the trends are set by what the players do to their games wither they play single player, co-op, or online multiplayer.
Xbox has taken that data and based their whole game outlook on it so far, and people are rejecting it not embracing it. If they embraced what their heritage is as a console and as a part of a giant software company known back in the early days for pc gaming they would be in a better position.
Games as a service only works for certain games and is never determined based on trends, after a series of games has been established. F2P models in retail games only sours the pot.
Which is why so many online games this gen have failed and only a handful succeeded for new IP's. GTA V's focus was never online when they launched campaign's for the game and launched it, hell wasn't even ready or that great to play in the beginning when it launched.
But as people played with it and gave feed back it took on a life of it's own. ANd rockstar adapted to what people were doing and embraced the free form nature of the community.
XBox is doing the opposite they are taking preexisting franchises and shoving new pay/ life extending models into them to try and create a community, not letting the community form organically.