If you asked me to name one genre of game Square Enix could not do well no matter how hard they tried, it would be a survival shooter. I happen to love most Square Enix games, but their shooters are always been developed by their western affiliate studios like Eidos Montreal and (formerly) IO Interactive, not Square Enix's own internal teams.
However, Left Alive is by SE Japan themselves. And, honestly, my initial hunch was correct. Left Alive is barely worth playing. It does nothing well, and most things very, very poorly. The gameplay is terrible, the story is utter nonsense, the mech battles are confusingly bad, and the crafting system is clunky and unhelpful.
Add an overabundance of crashes and poor graphics optimization and there are no real redeeming qualities to Left Alive. Which is a disappointment, because the concept behind the game – a survival shooter set in the midst of a warzone – is a pretty decent one. The execution is just completely terrible.
I couldn't find a single positive thing to say about this game other than "it tries." However, it does not succeed.
Save yourself the trouble and go play Metal Gear Solid V: The Phantom Pain.
Honestly, even Metal Gear Survive is more worth your time than this one.