I do think it's actually very difficult to be a studio that can make a really successful singleplayer centric game.
Generally the types of games that sell best are:
1.) Ones that match the conditions of the market.
2.) Ones that are so exceptional that they succeed despite the current conditions of the market.
Microsoft doesn't have a bench of studios with strong singleplayer legacies, so it's much harder to go and succeed on that front.
Like yes, Guerrilla managed to go from having relatively poor reception to making a very well received game, but it's not like Sony didn't dump a ton of partners and titles along the way getting to that.
Now, I agree with the person who said that first parties, especially outside their flagship titles, are often best served making games that expand the audience for their platform instead of trying to compete with $30+ billion market cap juggernauts, but you still need the actual talent to do that.
Similarly, while Zelda is a huge success, you don't see Nintendo wheeling out a game like that every year. Zelda took five years to develop and is on the Switch in part because its development cycle went much longer than expected. In between games like that, they actually wheel out a lot of... service games like Splatoon, ARMS, Mario Kart, and Smash.
Now, I think Microsoft's first party line-up is actually pretty bad. They're not selling anywhere near what they used to, nor are many of their games resonating with niche purchasers, but that's something they can't really change quickly given games take 3-5 years to make these days.