I've been playing some hours of Phoenix Point now, about to start a new game because I lost too many soldiers which turn out to be very hard to replace. But apart from such minor differences as how hard it is to recruit soldiers, or how exactly the tech tree looks like, Phoenix Point is essentially the same game as XCom 2. The basic game flow is the same, a geoscape with resource management, and turn-based tactical fights against aliens. In detail there are things I like better in XCom 2, and other features which I like better in Phoenix Point. But for somebody who hasn't played either, it doesn't make much of a difference which of these two games to pick up.

That leads to interesting subject of fungibility of games: In how far can I replace game A by game B of the same genre without it making much of a difference? Steam alone has over 30,000 games on it, and it is safe to say that there are far less different genres of games. Depending on how narrow or wide you define genre, you can find dozens or even hundreds of games of the same genre.

I am currently downloading Final Fantasy XV from the Xbox game pass for PC. If I consider Final Fantasy XV to be a very different game from let's say Dragon Quest XI, the Xbox game pass cannot provide me with all possible games. But if I am okay to just play any reasonably recent and good JRPG, a service like Xbox game pass for PC is maybe all I ever need. If I feel the desire to play a JRPG, and I have access to FFXV as part of an ongoing 4€/month subscription, do I really need to go to Steam and buy Dragon Quest XI for €60 anymore? If I want to play a shooter, should I bother with installing Blizzard's Battle.net and pay €60 for the latest Call of Duty, or am I equally well off if I just play Gears 5?

The fans will always insist that game A is much better than game B of the same genre. But of course you'll also find the fans of game B, who claim that it is much better than game A. The more casual a gamer you are, the less of a difference it makes which of these games you play. And then the convenience of a single platform with a single and relatively low monthly cost compared to individual game purchases is a big advantage. The monthly service doesn't have to offer 30,000 games in order to compete with Steam, it only has to offer enough games to cover a variety of different genres.