Fitting with the idea of a language shaping our thinking/neurological processes, I think they were going for the idea that we had to learn the language from scratch rather than merely be provided a translation--and at any rate our own Earthly languages often don't translate in a clean A=B fashion in many areas (cultural nuances, and yes different ways of thinking make these translations less than clear), and so I imagine this is very true with translations between any human language and the heptodes' (where a "sentence" is a single holistic circle that can be written or read in any order--I know of no human language that evolved in that fashion).
They mentioned at one point the idea that people learn other languages most effectively when they are immersed (where they have to listen very hard and pick up on whatever cues they can from native speakers, with no help in their own language), and indeed forced to "figure it out on their own" to a large extent (they might still supplement that with classroom learning in the host country, but ideally that is conducted solely in the target language too--just with effective techniques of visuals, demonstration, and directed exercises given the students). The heptodes were providing as much of an immersive experience as they could with the on-board visits.
So for all we know (and it's plausible for sure), they may have already figured out at least the rudiments of our languages from monitoring our broadcasts (though still lacking cultural contexts and "immersion" themselves), at least enough to be capable of communicating with us in our languages. But using our language in their "classroom" would not have taught us as effectively--and probably wouldn't have succeeded in teaching us to "think in their language", which was the goal of imparting the thought process changes that came with really knowing it (i.e. being able to think in it as second nature). They forced us to stretch our minds to figure out their language in its own terms, and the very fact of their sudden and dramatic visit to our planet motivated us to do exactly that to figure out what the heck was going on--with an extreme curiosity and urgency.
Given their goal to teach us to think in their language (so we could supposedly also perceive time holistically as they did), all the things they did actually make a lot of sense toward that purpose. The "why" of "so you can help us in the future"? We're not given any more than that. It could be that we simply join in some galactic enlightenment movement down the line, that ends up helping everyone (particularly at some critical juncture in galactic history 3000 years from now, when we ourselves may be an emerging interstellar civilization joining the galactic community)--it may not be technological or other strictly material help at all. They may be "uplifting" us (akin to the concept in the Brin novels) for purposes that will benefit them, and hopefully be of mutual benefit. We have no idea, except that fostering in us the ability to see time the way they do is apparently key to it.
But “understanding” is a three-edged sword.
Who cares about seeing the future? All the fun stuff in life (sex, skiing, driving a fast car, reading a great mystery novel, eating a great steak, drinking a great red wine, falling in love, hearing a song) has absolutely no connection with time, unless it's the gradual unfolding of an event (skiing down a trail, tasting a steak, etc.).
Why is "overcoming" the distinctions between present, past, and future seen as so desirable and so advanced? It doesn't cure cancer or stop aging or prevent death. It's just a weapon. It's not skiing.
If I know English, then I can enjoy Shakespeare or Wordsworth or Keats. English has rhyme, assonance, and meter. You can't write a sonnet in Alien.
If language exists ONLY to convey information (maybe like a programming language), then I can see how Alien would be a superior language, but I prefer "shuffle off this mortal coil" to "death process." The aliens talk like robots talk. Can they write poetry or have slang or come up with a Cole Porter song? They can see the future, but can they craft a pun?
It's not mind blowing...unless you are simple.
It's not smart...unless you have a learning disability.
It's not one of the best sci-fi films in our recent history...unless the recent history you speak of is limited to the last two months of 2016.
It's a bad film. Badly written, badly acted, badly directed, badly scored, badly edited, and badly designed. Its lack of originality is matched only by its pretentiousness. I can often find something redeeming, however small, in many of the most mediocre films of all time, and yet I can't find anything good to say about this one.
Wait...it wasn't 3 hours long! That's good, right?
Oh, and also, it provided plentiful entertainment for those wonderful folks who like to think they enjoy "smart" films, so they can come up to me and say the same comical, tired, and pathetic lines over and over again:
"You just didn't get it"
"You're not smart enough to appreciate the concepts"
"You should watch Transformers instead"
LOL! Every time. After all, being a stereotype, means being unable to even consider you might be a stereotype. It's sort of in the job description, right?
(Wait, I've used that Transformers line myself in the past. Oh snap! Guess I might be a stereotype. That's depressing, now that I think about it. Bummer.)
NB: If you like SF, read the short-story it was based on.