'completion' is only a useful benchmark if you are wanting to ship a finished product. That is not the business model for these kinds of games... they're all about keeping subscribers happy and people have been happy paying for updates with additional scenes and characters. Love + Second Base is literally an ever-expanding soap opera where each new update brings new scenes, new characters, new social structures. These games do not need to ever 'finish' just as World of Warcraft doesn't need to 'finish' as long as you keep adding new stuff, people will be happy.
I suspect the issue is that, at some point, a technological decision was made that made that model impossible. I suspect these kinds of technical reboots are often done in an effort to give games room to grow. The problem is that, with a game this old and with this much content, getting rid of all the content is a death knell as it will now take years just to get the game back to where it was at the end of the last update and those are years in which existing subscribers can get bored.