The movie is a complete joke - so this review is just a bit of fun I used to think that the truly imbecilic James Bond film Skyfall had the stupidest plot I'd ever seen. I still think so but this was definitely a challenger for the crown. I'm not going to mention the variable-quality acting (including Pratt's usual wooden turn), the OK SFX, the seen-em-before monsters, and the dull clichéd father-daughter AND son-father relationships in the same film. I don't care how good other stuff is (in this case not very) if you can't manage to employ writers to produce a story that begins to make sense, why bother? So I'll just have some fun with the stupidity of it. There's so much of this, if I don't restrict to a tiny fraction, this review will turn into War and Peace.
So, future folks have invented a wonderful super-magic transporter to take people through time. For some reason (which got a long explanation that made no kind of sense) it isn't actually that wonderful at all and will only go from A to B (B being a single relative point in the past, let's say 28 years ago) and back again. Invaded and overmatched by (weaponless but quite toothy) aliens, these future folks have decided for some unknown reason that the best use of this machine is to transport untrained civilians from the past (let's again say 28 years ago - well, why not?) to fight against an enemy which has already destroyed almost all their highly trained, professional troops and apparently all their ships, aircraft and armoured vehicles (no clue how they did this with just teeth and claws). Why can the civilians not be trained before going, why do they get dumped at random into a rooftop swimming pool and why are they not offered the protection of e.g. Tanks which the aliens have no way of penetrating? Just a few of the obvious questions that occur. The writers have given up explaining stuff by now but never mind - these are the least of our stupidities. Why in fact do ANY of this stuff, rather than sending their well-trained, well-armed troops back to the time when the threat emerged (they know pretty well exactly when and where) and nipping it in the bud when there are hardly any budding aliens to nip? Guess what, still no explanation - there couldn't be unless you employ decent writers to make one up, in which case you might as well have them write a sensible plot in the first place.
Moving on, the whole movie revolves around developing a toxin which can kill the aliens. This is done in the future, presumably because their tech is better (as it no doubt would be) but for some reason these future tech giants cannot then synthesise larger quantities - this has to be done by us Neanderthals of 28 years ago. So far so not entirely stupid, but the toxin THEN is supposed to be transported back to the future (by which time almost all humans have been exterminated and the whole planet surface is knee-deep in aliens) before deployment. Why? (No explanation.) Alas when our brave hero gets that toxin back to the past, the magic time machine breaks, so nothing can go to the future any more. Doom. Despair. Much wringing of hands, glum expressions and tearing of hair. But hang on, why not just stockpile it and use it when the threat first emerges (which should have been the plan in the first place)? (And, by the way, when Earth's population is still around to appreciate not being exterminated.) Then they realise, ooh they CAN!!! (or, this plot being what it is, they can do something stupid which will have a similar effect).
Turns out the government budget won't cover the couple of thousand dollars required to do this (of course not - after all they'd only be saving pretty well all humanity) as the money's already been spent sending people forward in time to be dropped in swimming pools and slaughtered. So it's all on the shoulders of our wooden hero, his dad and a handful of others, charging to battle on snowmobiles. A silly chain of deduction leads them to locate the alien spacecraft. (How do they know there's only one rather than a fleet? - of course they don't and yet again no explanation.) At this point, almost all the aliens are destroyed by planting a bomb on the craft. But hang on, what about that magic toxin which the movie was all about? Got to use that, right, so before deploying the 100% effective bomb, they go into the craft and use toxin to kill a handful of sleeping aliens, which results in lots of others waking up, escaping and having to be excitingly shot. OK, so now they got that out of the way, they can plant the bomb, which they do very heroically indeed.
Do not watch this if you value your mental health. If you are already a moron, you should be fine. In fact quite a lot of them have already given this rubbish a high rating.