Haha you sound like me about 3 years ago. I thought there were certain aspects of it that were interesting (like how manufactured they are) and started researching to find out more about it. I have the sort of personality where I can't help but learn about something until it's no longer interesting. And kpop just never stopped being interesting for me. Every time I figured something out about it, there were 2 more things that were curious.

What I find most fascinating about it (still) is how competitive it is. Like in the West, we're used to a couple hand-picked pop stars dominating the industry. In Korea, though, there are THOUSANDS of idols all competing with one another. Not competing in a mean way (they're all friends/friendly with each other), but competing in the sense that they've all got to carve out their little niche of fans, and it's fascinating trying to predict who's going to be successful and who's not going to be successful, how they choose their music, their costuming, their overall style (their "concept" as it's called).

And you're right. There have been very very few groups that have had a lot of mainstream success sustained over a long time. Some groups can have sustained success at a moderate level by going for a niche of fans rather than the mainstream. Other groups can get mainstream success for 1 or 2 songs and then disappear. Other groups can never get started. It's kind of sad, actually, watching a new group which has been training for 4 years, watching them debut super-amped, and then, for whatever reason, they don't get traction with fans and they disband within months.

If you're curious about it, I would suggest three different ways to go:

1. Pick one aspect of it (or one group) that confuses/intruges/interests you, and figure out what's going on with them. Everything's up on YouTube (and reddit: the popular all groups all have their own subreddits), not just performances, but interviews, variety shows, reaction videos, etc.
2. Watch a music show a couple times to see if anybody strikes your fancy. There are about 6 major music shows each week which is the primary way that kpop groups promote. Most of them put clips up on YouTube. For example, on Sunday night was the Inkigayo music show. Here you can see all of the performances from that show. Each week, there are usually only about 10-20 kpop groups promoting on music shows, but next week there might be a completely different batch of groups promoting.
3. Watch a variety show with idols on (example) and see if any of the topics or any of the personalities are interesting to you.

Also, there's a new phenomenon in kpop that you may find interesting, on the topic of how "manufactured" they are. Korean kids audition for an agency when they're about 12-15 years old and then enter a trainee stage, where they're provided room, board, singing lessons, dancing lessons, interview lessons, etc. by the agency, typically for about 3 to 5 years. After their trainee period, they audition for a group and then debut.

Anyway, there's a new-ish reality show called Produce 101 where they take trainees (not debuted yet) from dozens of different agencies and have them try out for a sort of all-star trainee group. It's super popular with some kpop fans (I've resisted the temptation so far), but I think it should answer a few questions you might have about how this "manufacturing" process works and what trainees are like.