Because the current implementation includes completed series that do have an ending. I'm not sure why you'd want only series that are currently updating considering you can just as easily read something like Bleach for literal years without ever hitting the release limit if you pace yourself on the same weekly schedule as when it was released. If a person has no self-control to avoid binging, then I guess the option does have some use for them? My mistake.

Why is there now discussion about boolean filters? I recently quit my job as a software dev. Let's not get into scope creep so quickly when you guys are not even the devs yourselves.

Boolean filters may seem easy enough to implement but they require evaluating the database's existing information as regular expressions if you want to retain any modicum of CPU efficiency. This opens a massive can of worms especially with regards to data integrity and security. You can't think about coding only in the context of what a module can do; you must consider what knock-on effects that module will have on the overall architecture.

I'm not saying RegEx is the only way to do boolean search logic, don't go at me over this. But if you're going to make a whole custom implementation of boolean search logic, you might as well hire a new dev and redo the entire website because it won't be cheap or easy. This is why many dedicated search engines have absolutely terrible conditional searches... They can't be bothered to put in all the effort. If they won't do it, I don't see why MU should be any more obliged to do so.