Well, first of all, the Gamepass initiative isn't event exclusive to Xbox anymore since they announced it for PC recently. Sure, it certainly could be an incitive to get the console but after looking at how "good" the catalog of exclusives the Xbone had throughout this generation, then I'd say they'll have to up their game by a considerable notch.
PS. : Using their usual trio (Halo,Forza and Gears) won't be enough this time too.
The reason MS included the PC is because this service needs more subs. Also the games included for the PC and the MS console are not all the same. The thing is, by having an ultimate sub, it can make people who have a PC also consider getting the MS console because they are already subbing for the PC.
You are missing the point, getting Halo, Forza and Gears for a sub price is pretty strong especially if you love all 3 games then gamepass is pretty much free and you get 97 other games that you also may like.
Not only that but gamepass pretty much pays for games like Flight Simulator and other obscure games that on their own probably would not get funding but now because of gamepass you will see way more of those types of games. A lot more singleplayer focus games will also be coming to the service from MS as well as some IPs from their collection due to gamepass.