>> I am surprised Firaxis didn't work on an X-Com 3.

Firaxis didn't but Julian Golop's company, Snapshot Games (discussed in the article) published Phoenix Point which is kind of like X-Com 2.0.1:

https://store.steampowered.com/app/839770/Phoenix_Point/

That one unfortunately got caught up in publisher politics as they had a very successful kickstarter but then broke promises to backers because Epic offered them a lot of money for an exclusive. I think the game would’ve been more popular if it hadn’t had the distraction of many of their biggest fans feeling used.

https://www.rockpapershotgun.com/phoenix-point-becomes-epic-...

The long war mods are X-Com 3-ish - they are extensive!