TBH the smart thing to do when discovering a serial killer server is to call the police. It's the reason why the best endings are called 'bad' endings. MC being dumb is actually intentional, bonus points for making them a journalist. Doing anything for a story? Classic journalist mindset.
Angel and V's (arguably Misaki as well but more on the co dependence part) routes do 'we can make each other worse' and 'toxic co dependence' better than Ronin imo. V's route actively ends with you becoming a serial killer as well and joining him on his kills (he actively encourages it, and you don't encourage him to stop rather you enable him). Angel's ending is You clean her up after she kills her manager with a point-blank shotgun before falling asleep in her bed together, and it's heavily implied that you're her emotional crutch . Misaki is a mention on the co dependence part because her whole route surrounds you being an emotional crutch but the ending points more towards 'you can fix them' and isn't as toxic as the rest.
Ronin is just your standard ******* BF who isn't actually into you but likes your attention. Which is the more boring option, which is always the most popular option because it's easier to head canon him doing differently. Combine with being an edge lord, and he's the perfect option for those who say they like toxic but can't handle anything worse than being ignored.