I think what you're really arguing (not trying to put words in your mouth, but I think this is an accurate rephrasing, please correct me if you disagree): Microsoft makes most of its gaming money from software sales and is seeing growing sales from GamePass subscriptions, which sells more on Windows than Xbox. Therefore, locking exclusives just to help sell Xbox consoles is a wasted opportunity to sell to all the PS owners, which wouldn't really adversely affect their core sales and business model around gaming and subscriptions anyway. In fact, selling to PS exposes more users to their games and with gamers moving toward Windows/PC/other gaming, better to have that exposure than avoid PS just to help market-failing console as a shrinking userbase in a static-at-best overall console market.
So I'll sum up my response here, by just making my general argument clear because it's not like I really disagree with you. My stance is more like those points are kinda moot.
Very simply, what gamers would Microsoft even potentially be trying to attract with exclusives? The majority of their gaming business IS still coming from Xbox console users (on Xbox One and Xbox Series). That's where most software sales and most GP subs are. It'll be a long while before windows overtakes that. With exclusives, my thing is that after decades and decades, consoles have never succeeded in selling to significantly more new gamers with the early 2000s setting the peak. They've also not really succeeded in taking a significant amount of market share from each other. Like the Nintendo Switch is selling about as well as their handhelds (minus the 3DS) always had + the few tens of millions that consistently bought their home consoles (the Wii being a major exception (Nintendo was doing really well when they were selling both the Wii and DS)). Playstation started at 100 million and seems to have settled now around 120 million. Xbox started at about 30 million and has settled around 50 million (which the series is still on track for IF Xbox were to do a mid gen upgrade this year and didn't release next gen until 2028... which I feel has been all but confirmed they won't do, so if there's an early next gen they'll probably see lifetime sales for the series between 30 and 40 million). The most they managed to steal was during the PS3/Xbox 360 which I really think was more on the massive price difference between the similar spec consoles. Then Xbox made same mistake Sony did and lost about 30m of those Xbox 360 sales at the onset of digital and locked down libraries.
I will just outright say, I don't see consoles growing even within the console market anymore. I think Microsoft SHOULD try to grow console sales, but to do so they need to reach outward and pull people into their console and Xbox ecosystem. I don't think Microsoft is doing enough here to target non console gamers. They're actually failing a lot to reach new audiences. And so is every other console on the market. Based on what I see, I don't think exclusives work here. Speaking of leveraging strengths, how is it not a strength for Microsoft to leverage its now massive first party content lineup to fuel Xbox more through making these games more available. I'm really not saying anything specific regarding exclusives here other than that I don't think they matter going forward (as in Microsoft can keep doing some and only make a handful multiplatform; I just don't think exclusives are going to build up their market share in the console market or wider gaming industry). Microsoft shouldn't abandon trying to grow Xbox console sales, but they should revisit how they plan to do so. I think they could reach a lot more new gamers with a marketing strategy revolving around all the exclusive
features Xbox consoles offer, their value, and most importantly reaching out to appeal to non current console gamers. Xbox as a brand and ecosystem and platform needs to do a LOT of growing in the console, PC, and Cloud markets.
You speak about the importance of controlling the family/living room space and I agree. But does any home console? Or do smart TVs and streaming boxes? Amazon not too long ago bragged about selling 200 million Fire TVs. The Xbox One had the right idea that they couldn't just compete in the console market (which is now entreached and stagnating), but the wider home entertainment market. Unfortunately the Xbox One had the worst pricing and messaging for this and seemingly traumatized the Xbox team from acknowledging that this generation. The Series S should've been much better positioned to appeal to families that wanted a home entertainment device for all their home entertainment needs. It's a big reason why I think they can't abandon the SKU or the keystone idea moving forward. Microsoft should try to grow their presence in families and homes as an entertainment platform they control (so they aren't under the whims of others like in Mobile), but again, I don't think that necessities exclusives. I don't think we really disagree on what Xbox should be trying to achieve. I think we just don't believe in the same how. Which granted Microsoft will do whatever they want (usually not enough) and reality will play out as it does.
I think their failure to respond to Steam OS is due to the same mindset as their releasing what could be exclusives on PS -- they don't appreciate the value of controlling a market. For a company with MS experience, I find this bizarre. My best guess is it is a consequence of the prior problems they faced 20-30 years ago when the government successfully attacked MS for monopolistic behavior. But these decisions by MS go way past that to just being bad, destructive strategy.
That one monopoly case is definitely still holding Microsoft back, and really because that's still their reputation all these years later. People hate and don't trust Microsoft to a level that doesn't really match public feelings of similar corporations who have even tighter control like Apple and Google. The ABK aquistion really showed this. Historically it'd have passed no problem, and for the most part it did. Microsoft did their rounds and appeased pretty much everyone. The roadblocks came from places that really just wanted to make a spectacle of blocking Microsoft from a big purchase. I remember even people who hated Xbox calling the FTC and CMA out for grasping at straws and mostly using stalling tactics or ignoring competitors. And harkoning back to the exclusives, again what I think about them doesn't matter. It's what Microsoft does, and there is clearly a shift before and after the ABK case at Xbox for how to handle exclusives. I don't think Microsoft is done growing in gaming and I do think they weren't expecting that much of a push back from government regulators based on exclusives, so now they're either afraid to push too hard with them or trying to diminish their importance in their business or maybe it did just line up with their analysts saying they aren't important and them wanting more money (or likely it's a combination of all of the above).
Regardless, Microsoft is clearly terrified of risking coming under fire from government regulators, and as a result they are the most careful to limit their control over their markets. Again it's interesting because companies of similar sizes exert more control and are on people's and regulators radar less. Apple and Google are only just now starting to get attacked and that's really slow moving. The thing is, Microsoft does NEED to be more aggressive in the markets they exist in to succeed. Again, I don't think they should give up on console hardware. I just don't think being aggressive in that market and success is based solely on exclusives (like they could try marketing for once). They need to be far, far more aggressive on PC and get their offerings up to snuff. They're moving incredibly slow on cloud and mobile they don't even have a platform foothold in because they weren't aggressive enough with the windows phone and now have to march to the whims of Apple and Google.