Responses in bold
The problem is that there are very few independent AAA devs left these days. Their 2nd party division is already working with some of the remaining ones like Avalanche and IOI (while Sony has already snatched up deals with alot of the new AAA studios that have recently opened), leaving Xbox with very few remaining potential independent AAA studios to work with on 2nd party exclusives. Their 2nd party division needs more AAA's in the pipeline than they seem to have currently, and it would be alot easier to make 2nd party deals with AAA studios which are owned by other publishers if Xbox was willing to wait say 3-6 months for the game to come to Gamepass.
I've never really agreed with this Tbh. There is multiple new AAA studios opening every year, that is on top of the already dozens of known AAA developers and there's dozens of developers who could easily go AAA if they had someone to finance them, there's dozens of assistance studios like Certain Affinity who have hundreds of employees but need someone to take a bet on them for a singular project.
Microsoft is doing that now, Certain Affinity is doing their first ever AAA under XGP, Oxide Games is a studio that nobody had really heard of but their IP with Microsoft is listed as AAA, Brass Lion lists their project with Microsoft as AAA, then there's studios as you listed such as Avalanche who have multiple studios or IO Interactive who created a new studio precisely to create an AAA with Microsoft, there was the rumoured MMO which was by a studio that once again nobody had ever heard of but it was AAA, later found out that Microsoft isn't involved anymore but nevertheless it's yet another example of a AAA studio popping up out of nowhere.
There is also studios like Asobo who nobody considers AAA but they just released the AAA Flight Simulator, there's dozens of studios like the above examples but someone needs to take a chance on them, I think what is really true is that there's not many known AAA studios left, as in, the popular ones that everyone knows about, which I can sorta see, but that doesn't mean there's few AAA studios or AAA capable studios left in the entire industry.
This is without getting into all the AAA studios that Microsoft now has under their belt along with the studios which are expanding to be AAA, studios such as Obsidian or InXile who were not AAA until Microsoft started financing them, InXile in particular was nowhere near AAA. Undead Labs and Ninja Theory will likely be AAA too, there is so many studios like that out in the industry, AA ones who could easily do AAA if someone backed them, or studios which expand such as Playground or Arkane opening separate studios.
I don't recall Xbox having any truly big licensed exclusives 7th gen. Star Wars Kinect doesn't exactly count since it was a Kinect game which automatically limited it's sales potential. Your Marvel's and your Star Wars' and your Indiana Jones' and such can move alot of copies and hardware if the game is made well and marketed well by Xbox.
That's sorta my point though, Xbox 360 didn't have any big licensed exclusives and yet did very good in sales, PS3 didn't have any big licensed exclusives, Wii didn't, Switch doesn't, PS4 only had 1 notable big licensed exclusive and it would have still been a 100m+ selling console without it, no doubt they can be awesome and they can push some hardware but so can a lot of things.
Of course I agree that Xbox should be building up their own IP, but that takes time. Their biggest IP of the past, Halo, only sold like 13m copies on it's biggest game (Halo 3) compared to 20m+ for 5 Sony IP this past gen, while other Xbox IP sold less than Halo. Gears did like 7-8m on it's biggest game, Fable did like 6m on it's biggest game. Forza was selling like 6m copies at most before this past generation, and while Forza Horizon's explosive popularity growth over this past gen has allowed 20m+ players on the series now, we don't know what that comes out to in sales since Xbox doesn't announce sales these days, just player counts. Outer Worlds has sold like 4.5m as a multiplat release, sequel may sell less as an Xbox exclusive. The fact is, many of Xbox's biggest IP's of the past were only selling like 25-33% of what 5 different Sony IP's are now capable of moving.
Xbox's acquisition of Bethesda did at least give them one studio that has proven themselves to be consistently capable of 20m+ sales, but that is still 1 studio for Xbox compared to 4 studios for Sony so far. Xbox has a lot of catching up to do on 1st party popularity growth, and big exclusive licensed games in the meantime could help with growth overall platform growth while their 1st party IP's are hopefully growing in quality and popularity.
Sure, Halo 3 did only 13m compared to Sony's 20m+ sellers in the last generation but Xbox took an absolute battering in the last generation and squandered all their brand build up, Sony didn't, Sony's PS3 era ended very strongly and they entered the PS4 era very strong with multiple extremely high quality developers, they didn't fuck up their marketing, their focus was clear, Xbox's wasn't and it caused them to lose fans, lose faith in the brand, they were running around like headless chickens and releasing half-baked products.
Nowadays they're a lot more focused and have a wide range of quality developers working for them either internally or externally, if they build great products and don't fuck up their brand again then people will come, it took one The Last of Us and one Horizon to turn them into big products cause they were simply great products and Sony didn't screw their brand, if Microsoft does the same, the people will come, whether it's Indiana Jones or Perfect Dark.
Though sales is pointless nowadays cause of Game Pass so I don't know, no point worrying about if they reach 20m+ sales or not.