Short answer: Yes, Skyline was really that bad.
Long answer: Skyline COULD'VE been awesome had the directors taken the time to craft a coherent story that actually and properly integrated their cooler ideas rather than just leaving them strewn about the film like a child leaves his toys scattered about the floor of his room. Also, the film was marketed as an alien invasion epic, yet the ENTIRE film takes place in a high rise apartment building. You're also never given any explanation as to why the invasion is happening, or *SPOILER* why the blue light gives humans increased strength (An idea only used once after it's introduced). There is also a twist in the last two or three minutes that's given no build up or real resolution. It just happens, and the directors expect you to just go along with it, like so much else in the movie. I think Ben Kendrick of Screen Rant says it best: "[Skyline] comes across as a big-screen B-movie with a convoluted plot and too limited of a scope to make the audience feel the worldwide alien-apocalypse that’s supposedly unfolding in the film."
And to take things back to Battle: Los Angeles, Sony actually considered suing the Strause Brothers, the directors of Skyline, because the effects company they own was hired by Sony to develop the effects for Battle: Los Angeles, and they never told Sony about Skyline. That's why the film looks so similar.