It started off really well and was good until the end but then it became just flashbacks and fillers. Also the killer became very predictable by the end and was not impactful at all. For some reason I started to feel cringe watching the ending episodes.
Why does it feel like most of them are those dramas which didn't have romance tag.
Because I think more than 90% don't have romance tag, most of the Kdrama audience watch romance or zombie dramas and that's why non-kdrama watchers think kdramas are all about that.
https://www.asianjunkie.com/2018/02/11/lee-jin-wooks-accuser-sentenced-after-overturn-on-appeal-that-used-rather-odd-reasoning/
Btw I agree with your last statement