Spiders was written as a culmination of three typical movie plots: alien invasion, government conspiracy, and monster attack. They took successful plots and threw them together to create a sloppy movie. It could have been pulled off better if they had chosen just two of those instead of all three. It seems like they only pulled in the alien aspect to justify why the spiders were growing so big, but they could have done that with the military injecting them with a growth hormone or genetically engineering them. I think it would have been more successful if they had gone with either alien spiders invading or a military project gone wrong instead of both.
The acting wasn't the best either. Sydney Sweeney played what was probably the least emotional 12 year old I have ever seen. Her voice was monotonous, having no difference between when she was happy, sad, or afraid. The military personnel also don't behave much like military personnel, particularly the one telling the main characters it's time to evacuate the city. The didn't sound like they had any authority in their voices and weren't confident in their delivery. And of course there is the scene with everyone running out of the subway "screaming" while there are a bunch of rats running around. Those were some pretty half-hearted "ahs" and didn't make anyone believe they were afraid.
There were also things that just didn't make sense. Granted that some of these could just be personal preference, these are things that I think could have improved the movie if they had been done differently. I feel like the only reason for the Russian satellite to be involved was to give a reason for the spiders to be in New York. That's totally acceptable. But why were the spiders sent to space in the first place? If it had been purely aliens instead of a government project then we wouldn't need more justification, but with the military being involved we need a little more reason behind it. When Patrick Muldoon sees his daughter in the window and a man comes from behind to pull her away from the window I felt that could have been done without. I understand they were going for a panic factor, but the military personnel just didn't want her to leave. I also think it was unnecessary in whole for Muldoon's character's immediate instinct to be to distrust the military without much of a reason to run. The military also had questionable actions--what was the point of doing whatever it was they did to the other NYT worker on the street before getting in the SUV and why did they disguise themselves to rob Muldoon's wife instead of just approaching her and asking for the eggs as part of the government? It was completely unneccessary and didn't make a whole lot of sense, along with why they killed the people in that building. There were a lot of things that could have made more sense if they had just explained them more, but they didn't take much time doing that. I also didn't like how easily Muldoon was able to cut through the queen's web. It was explained that it was bullet proof, and while I know knives are capable of cutting through things that are bullet proof, I think he it should have taken him a bit longer to do it, especially because his knife most likely wasn't the best quality. And of course, there is the matter of the spiders. I enjoyed the spiders, but there were too many times when Muldoon and his family would get away from them. Spiders are fast, and there was no good reason for them to not catch up to the characters. They took a few steps and then roared or hissed or whatever before moving on, but they only did that with Muldoon's family and not the military. And if the spiders could break down the metal door in the subway when Muldoon and his wife first find the spiders, I'm pretty sure moving boxes and crates to block the spider from getting in the window wouldn't be much help. I understand that they wanted the main characters to live, but they could have had a better variety of escapes other than the roar and hiss and finding someone else to kill. And the queen? I get why they had Muldoon be the one to kill her, because he's the main character and all, but the military was hitting her with all sorts of guns, grenade launchers, and even tanks. Not only did those not effect her, they didn't do anything to her. And when the subway train hit her, it shouldn't have exploded. Crashed and created shrapnel? Sure, but exploded? Those things run on electricity, not gas, and while I could be wrong about this, I'm pretty sure it would just be a big crash instead of a big boom.
All in all, I think the movie had potential, but they tried to do too much with it, had poor justification, and poor acting, causing it to fall short in every area except the monster attack.