Understanding sentences without subject or object.

Today, I saw a video made by one of my former classmates from when I was living in Tokyo:



The phrase (すごく気に入りました) directly translates into English as only, "Liked a lot"; no grammatical subject nor object. However, the translation given in the video is, "I liked it a lot." Note the inclusion of a subject ("I") and an object ("it") that was not in the original, direct translation of the phrase. Technically, the phrase can have both a grammatical subject (私) and object (それ) in Japanese (私はそれをすごく気に入りました), but - unlike in English - they are not necessary, given that we understand the context of who is liking what. The phrase, すごく気に入りました, CAN mean "he likes it a lot," or even, "it likes him a lot," depending on the context in which it is spoken. (However, the common context of learning a language is the speaker being the subject and the object being known, so the translation of, "I liked it a lot" isn't too strange.)

In this way, Japanese is a really flexible and simultaneously annoying language. Of course, this is sometimes a problem for Japanese students who are learning English Being able to speak (relatively understandably) without either a grammatical subject or object in Japanese isn't a problem. Why, then, can't one do this in English? If it works perfectly well in one language, why not in another? Why NOT be able to just state, "Like a lot," without any problems? (And - in some ways - wouldn't it be fun if it were possible?) Although not often a problem in written academic English pieces, sentences sans subject and object (as well as sentences merely sans subject) often emerge, making some monolingual English speakers go, "Whaaaa...?"