My $5 cents:
1- Can you imagine real people really saying it? Which emotion the pure line of dialogue conveys?
2- Raw dialogues (like a ping-pong match of dialogue, with no description of feelings, no facial expressions, etc.) works better when the reader is completely inserted in the context. Sometimes it's better to elaborate by describing the reasons behind their speech (if your narrative person allow it, that is).
3- Do your characters talk all the same? Do you insert any mannerism? Are their origins, moods, level of education, vocabulary different and they show in their speech? How do you can tell them apart if you were only listening to their voices?
4- Intonation brings information about intention in real communication. You should mention or try to make pauses, use punctuation and other resources, to help your readers to get the intention hidden behind the words. Even the speed, length of sentences and length of the speech can tell whether a person is stressed, angry, happy or anxious.
I was told analyzing other’s works help creating your dialogue style, but mostly, make it true by imagining all intonations people are giving in their speech. Imagine every expression. Imprint their quirks and personalities by choice of words, speed of speech, length of sentences, and so on. This way the reader will them apart and easily “listen their voices”: a talker, a diplomat, a monosyllabic character, a pompous person, a gruffy one, whatever.
As for example I took away all descriptions accompanying the lines of the dialogue below. It’s a trivial scene with 3 characters. You can see the descriptions of their expressions and inner feelings in the novel “Never Date a Man in Pink” – Chapter 18. https://www.webnovel.com/book/14869790405897805
1- Tag the main feeling the line brings to your mind (joy, contempt, sarcasm, helplessness, surprise, etc.).
2- Check the full scene with feelings descriptions and body expressions and see if it matches.
1-Mr. Go! Dr. Kim!
2 -My dear Ye Rim-ssi! It’s been a long time since you’ve last sung this last song. Ms. Nam sings wonderfully, doesn’t she, Jun Hyeon?
3-Yes, wonderfully…
1-The songs were not to your liking, Dr. Kim?
3-Did you received my flowers, Ms. Nam?
1-Yes, yes, what a good taste you have, Dr. Kim! Beautiful roses! I really didn’t expect it, I was very surprised! I am so glad!
3-Did you really like it?
1-Yes, I love the flowers. They’re not to blame, you know. They’re just come into the world to bring love and bliss.
3-But… What a beautiful and intriguing way of thinking. Worthy of an artist! I hope it’s not just a beautiful thing just said by the sake of saying it.
2-You… You…
1-By the sake of saying it? By the sake of saying it?! Ha, how funny, coming from a doctor who tells someone else to write his apology cards!
3-Ahhhherm…!
3-So Ms. Nam, do you think my apology was lacking sincerity? It may sound cliché, but I’m a pretty busy man.
1-I don’t know what you told your secretary, but you certainly didn’t tell I’m younger than you, Dr. Kim.
3-Ahnnn…
1-But like I said, I really liked the roses. I admired them. I appreciated their aroma, the softness of their petals, and all their love. They had a difficult mission, when you gifted me with them and that insincere card of yours. So, I gave them another assignment: I gifted them to everyone who came to enjoy my performance this evening, and now they express my gratitude to these people.
3-Hey. Hey!!! Why are you like this?!
I hope it’s a good exercise. I'm not a master on it, but that's how I try to build dialogs.