If you want to say those adjectives like cute, late and so on, the 'to be' is already included in the korean words. To be cute - 귀엽다 너는 귀여워요. You are cute. To be late - 늦다 너는 늦어요. You are late. No additional 'to be' is needed and the words can be used for any personal pronoun. However if you wanted to say someone is a noun you need to use 이다 (ida) which is 'to be' in Korean. It is a rather complicated verb because it changes depending wether the word before it ends in a consonant or vowel. Informal low: 이야/야 나는 학생이야. I'm a student. 이야 is added to words ending in a consonant, 야 to words ending in a vowel Informal high (most used in daily life) Ending in a consonant: 이에요 Ending in a vowel: 예요 그는 의사 예요. He is a doctor. (그녀 - she) Formal low: 입니다 for both cases 우리는 위너 입니다. We are Winner. I - 나, 저 You - 너 He - 그 She - 그녀 It - 이 것, 그 것 (lit.: this thing, that thing) We - 우리 You guys - 너희들 They - 그들 는 (pronouns ending in vowels) or 은 (pronouns ending in consonants) are commonly added to indicate the theme of the subject of the sentence.

Yes, you can use only 귀여워요 if the context makes it clear who you are calling cute. So if the other person sent you a picture of their dog, saying just 귀여워요 is totally cool! "Cutie" is 귀요미 btw. Same goes for the 학생이다. Dropping "unimportant" words in Korean is very common and you can do it as long as the context makes it clear what / who you are talking about.