You can still get short games, you just won’t find them from AAA developers anymore because publishers want big games with bigger profits. Titanfall 2 was a great campaign even if short, but Halo 5 was the last short game we had and people threw a shit storm (rightly, it wasn’t near the quality of TF2 and had other issues).
If you want short games, the indie space has you covered. Always small games out there releasing.
And game devs have certainly not become inefficient, it’s just the standards of quality are higher. People still want more complex, better looking games. And I don’t mean just graphics; unique art styles are all the rage. Games like Balatro and Cruelty Squad prove graphics aren’t everything as long as you keep a cohesive style and have good gameplay to back it up.
Personally though I avoid small games. I’ve had my fill of them growing up, I’d rather play big games with open worlds and all that jazz. I want to be invested in these worlds not play and forget.
I believe for the first Outer Worlds it was multiplatform because it was published by Private Division (owned by 2K at the time), not Microsoft. Obsidian wasn’t owned by Microsoft yet when the game was being developed. Of course, it just makes businesses sense to release the sequel on PS5 too for more money from sales.