Why was it rubbish?

I wouldn't say it was rubbish, but I will say I was disappointed with it (as a life long XCOM fan). Primarily because the microgame (tactical squad based combat) was good but the macro game (the strategical game in the world overview) was weak. Base building was basically non-existent compared to the original XCOM games. Instead you stumbled across existing bases and "build" on of 3 facilities in them. The research tree was weak. A DLC introduced the "shooting down UFO's"-mechanic but overall all of the DLC was just focused on more different enemies and story lines and did very little to improve the worldview game.

IMO, it made the one of the biggest mistakes that games can make: It just wasn't fun.

Browsing the reviews now, it's full of people saying how hard they tried to like the game. Good games make themselves effortless to enjoy. Even quite flawed games cause people to look past any awkwardness or glitchiness if they're fun at their core.

It's hard to express what makes unfun games not fun. But it was grindy in the wrong places, and just felt awkward to play. The balancing and pacing was terrible, and it just lacked charm.

It felt like it took itself really seriously, and it projected an air of superiority by deliberately not choosing to do some things that made the 2012/2016 XCOM games fun out of a sense that they were too "dumbed down".

If you go into developing a game being "Not X", then you better bring along a game-changing mechanic, graphics, or something else that separates and elevates you above that game. And PP didn't have that.

I’m a big fan of XCOM, but I bought Phoenix Point and it just kept crashing mid-mission. Sucked all the fun out of it and I gave up.