Short sighted.
They're starting as a website because it's easier to manage across devices and regions until they can create an app store. Same reason why they're only starting with games, it's a simple thing to focus on.
You start off with a website that you can access the files from any region and it will detect whether you're on android or iPhone and download the appropriate version for your device.
Once they've built out the website essentially as a demo, they'll attract others who may depending on the size and traffic of the website put their games there exclusively.
Then once they've built it out, it'll act as the backend to their mobile app.
In time, they'll put non-games there too. And they'll work with different companies to get the app pre-loaded on devices.
For some reason people have limited vision and think you must immediately go from 0-100 rather than have a roadmap.
Internet Explorer had full market share dominance on windows... until it didn't...
As for why consumers might want to go to that site, maybe the games are available there early access, exclusively, discounted, or for free if you have gamepass e.t.c. e.t.c. there are lots of way to attract people to the site. Plus most advertisements for games take you to the app store, no reason why advertisements can't take you to the Microsoft site.
I work as a Product Manager for a small software company. I can totally see how this line of logic and this plan comes together in a white board meeting with a few people, gets turned into a slick presentation with a slide deck, and pitched up the chain to the decision makers. I can see the argument being laid out by people who are really good at story telling.
The problem here is if you just step back and think about the end state: Are people who use Apple phones really going to choose to go to a website and press a button to download an app that acts as a new storefront after they've spent their entire experience on Apple using the App Store? I get that they
could, but does anyone really think a lot of people
will do that? I think that idea is laughable.
Apple more than any other company has trained (some might say brainwashed...) their users into doing things the Apple way, because the Apple way is best. People who use Apple products are more resistant to stepping outside the box than any other group of users I've ever encountered. This is about culture and feelings, not logic. That seems to be a concept that Microsoft are incapable of grasping.
As for the Android customers, sure they are more open-minded. But they typically fall into two camps: People who just use the default apps and don't do anything outside the box, or people who want to tear the box apart for the fun of tearing it apart (enabling developer options, rooting, side-loading apps, etc.). For that second group, I've never seen them actually care about any of the apps they side load. They just do it because they like to tinker. Microsoft trying to appeal to a subset of a subset of users who they don't understand also seems destined to fail.
Or, maybe Phil and the C-Suite know this, but they need to look like they're trying something so they can ride out another couple of years seeing how this plan goes. Even if they know it's sure to fail, if they can get a couple more years of employment trying to make it work, that's a lot more money in their pockets.