I love when they adapt web novels to manhwas, but I hate it when the original web novel either disappears. I think I'd be okay even if it wasn't in English because then I could use google translate to get some idea of what happens in the novel.
It's just that there are times when the manhwa is clearly only telling part of the story. Granted, it's possible it's not in the web novel either, since without access to it, I have no way of knowing, but when it feels like your missing key information, it makes you feel like something wasn't adapted.
For instance, there's this manhwa whose title is variously translated as "The Heart-Rending Crime," "A Sinful Love," or "Sin of the Heart." It's a very cringey romance, the type where you ship the main character with almost any other character than the one the author wants him to be with.
But there's this one scene where the emperor of one nation (Ran Yi) is surprised to find the emperor of another nation (Ji Yin) there. Ran Yi, such a lovely, stable person, grabs the other emperor by the throat. Ji Yin says that Ran Yi can kill him if he wants since Ran Yi saved his life...which you'd think would be a big backstory. But the reader absolutely never hears about it after this.