Because they stop making the consoles doesn't mean people don't already own the consoles and will need new software to play....and the majority of xgp subs are Xbox one owners hence MS may feel obligated to develop for both x1 and series x for the foreseeable future (even past the 1-2 years)
At some point surely its buyer beware? Like we wouldn't recommend anyone buy a RTX20xx card right now as you can get the same power for less, or more power for the same money when 30xx is released. If you buy an Xbox one or PS4 after 7 years, and especially after they've already announced their successors, you should have an idea that you probably aren't going to get a big long list of new games like there were in the prevoius 7 years.
its shown across many different generational transitions so there is plenty of history of this happening. And most likely if you're buying in now, you're more interested in the cost of the consoles and want something on a budget. In that case you can spend years buying decently discounted XB/PS games, getting the games with gold/PS+ games, maybe a gamepass sub. The available catalog to you is huge - bigger than anyone that bought the console before you as its always growing.
There will always be a 1-2 year cross gen period too so you'll get your FIFA updates etc. Potentially this time with x86 common architecture those evergreen titles will be supported for even longer.
Even the gamepass argument. MS has a few hundred titlees on there. There are thousands of Xbox games. Plenty of choice to refresh the catalog for XB1 owners. But - I understand as they want to grow the service they may want to maintain a large addressable market. Thats a business decision they're free to make. I just don't buy that its 'consumer choice' - its MS choice which suits their business. I'd argue there is just as much consumer choice allowing me to play new games on new hardware rather than holding things back and not showing me what this new box I just bought can do because you're also still supporting older boxes. Where is the consumer choice for the early adopters? My guess is they know they'll buy it anyway so dno't need to worry about that. And after that first wave of early adopters, the non cross gen games will start coming in.