well if someone is obsessed with a particular manga but they've ran out of chapters to read, obviously they'd want a carbon copy of it hence why these typical plots exist. If you look at comments in this section of mangago, most of the questions are asking for similar stories to their current favourite story.
e.g.
"Does anyone know a manhua like Killing Stalking?"
"Does anyone know a manhua like 'the ranker who lives a second time?'"
"Can you guys recommend me some hardcore rape like boku no pico??"
No, the first reincarnation webtoon I ever read was in 2017. So, it's understandable for it roam around till mid 2019. But now the homepage consists of 3 types of comics. Manhuas with shitty plots, reincarnation types and the good ol hardcore yaoi. I like josei and shoujo but it's rare to find good ones
These reincarnation manhuas and webtoons are really getting out of hand. The main storyline remains the same in each of them. At this point, it seems that the authors are forcing themselves to write these type of webtoons. Its either father- daughter duo, emperor-empress/concubine or crown prince-some random chick thing going on in every damn one of these. Good webtoons are hard to find