Why does every "drama adaptation" out there take JUST the idea, and then make a new, worse story out of it?

I disliked the FL. She was ok in the beginning, but became really condescending at one point. She just carried herself with an attitude of self importance and she often overreacted/overplayed. I also feel like romance wasn't needed at all in this drama, as it changed Rembrandy's character profile, which was an uptight funny priest that I loved. But them drama scenarists gotta ruin every original story.

For the plot twists, they could've been done better.

Firstly, there were lots of hints that Redlyn was evil, indeed. But why didn't she appear earlier? She's supposedly the main villain, but she only appeared in the last 1.5 episodes and was quickly taken care of. It would've been better if she appeared half-way or, even better, at the beginning of the story and she acted nice to throw us off. And the last fact about her, that she was a seaweed spirit who evolved into a deity that was explained in the last 10 minutes when no one asked, was totally unnecessary. Please stop adding last minute ideas with no foreshadowing from earlier.

The...uh, "Evil One" looked like a small fry wannabe villain. I totally couldn't take him seriously with his chubby cheeks, he looked like an angry plushie. His acting wasn't much better, there was just nothing dangerous looking abt him overall.
And then his reason for killing and wrecking havoc was really disappointing...I was expecting him to have a reason to hate everyone and especially the Pontifix. But it was all for a childish promise Redlyn gave him with no deadline: that if he keeps killing ppl, she'll be with him in the end. Lame. Eff off, horny teen.

There were a lot of small plot holes.
It wasn't clear if Redlyn absorbed the power of the other Pontifixes as well. She's the one who gave them power to begin with, from what they say. As opposed to Rembrandy, which had deity's powers and got strong from ppl's beliefs. So why did she kill the other Pontifixes then? And even if she absorbed their power, what abt the population? Why did she kill the common ppl? And she kept saying how she decided to get rid of Rembrandry bcz he started interfering with her plan. What plan? What interference? Was there a plan before you decided to take his power??
Even weirder were all the over-the-top scandals Woo Yeon Woo was involved in as an idol. Ppl would start either suspecting some conspiracy against Woo Yeon Woo, maybe supernatural business or even they might stop believing the subsequent scandals altogether. There was just too much exaggerated drama that wouldn't fly in real life. Ppl are not that stupid and easily swayed as they were made out to be. A few - maybe, but not the majority.
And then the stupid idea that Woo Yeon Woo was a middle aged minion that pretended to be Woo Yeon Woo. Ugh, stop it with the silly "plot twists"! At this point, they're just cramming as many as they can for the shock factor!