I'm ok with suspension of disbelief, but this show treads in stupid territory. The aliens that effortlessly wiped away the strongest armies and the most advanced weapons on Earth, are unable to beat a few hundred survivors with light weapons. Their flying craft apparently have the offensive power of a WWI biplane (they can throw bombs but have a range of 20m or so, allowing a guy manning a twin .50 to take them down). Actually, they can be invincible, wiping out all resistance, or just fumble around and get pwned, depending on what the episode demands, with no coherence whatever. Oh, they also have micro probes that can morph into metallic insects or take control of human hosts, but they don't have radar and apparently cannot track a flying civilian plane.
The protagonist is insufferable. A sanctimonious ex-history professor who proves to be an exceptional soldier, a great leader and even manages to beat up an ex-con who certainly has been through ten times as many fights as him. The other characters are mostly just as cringeworthy.
So, there is no suspense because the enemy will always miss and be taken down by a peashooter when it matters, the characters are unrelatable and annoying... what's left? Exactly: nothing.