before_after Usually, first 60 chapters are unlocked/free. That pretty much gives an idea of the story, writing style, plot etc. 60 chapters are minimum 30 k words if each chapter is 500 words. Is 30 k words not enough to give an idea?
About the plot going haywire later? It's up to the author really. I do agree that it's unsatisfying if the story's quality decrease. But usually, a story has highs + lows. In the end, it's up to the author what he/she wants to do with her story. If you don't like, u can drop it anywhere u want.
Lastly, yes, constructive reviews aren't bad. The author must have a strong heart if he/she is posting a story pubically. Must be able to take criticism well. Instead of posting bad reviews that might give a heart attack to the author or make them cry (I know authors who spend days in depression after getting bad reviews or lose motivation to write including), how about thinking what each star means when you are reviewing it? When you are rating, the five stars have categories -- Writing Quality, Stability of Updates, Story Development, Character Design,
World Background.
Tell me... how many of the authors deserve 1 star in each category? If the plot is going haywire then, story development is bad. If character design seems bad, then that category deserves 1 star. When you are reviewing a translated novel, there's a translation category. I don't think that the translator is doing a bad job of translation. When does he/she deserve 1 star in that category?
You might be bitter because the plot didn't go the way you like or ML abused FL vice versa or the grammar is bad or the story development was horrible or the world background sucks. You might be upset coz ML did a stupid mistake and you want to drop the novel instantly. Then you review it in your bad mood and give it 1 or 2 stars. Then blame the author for deleting it.
Constructive or honest reviews are different than rants/spams in reviews. If you are badmouthing an author, remember it's a person with a heart. Authors also need to steel their hearts/minds and accept criticism. Criticism are good to improve/motivation.