It's...rather sad you think of it like that.
A lot of the bugs come from old, shit coding, and it's a massive headache to actually sift through a lot of that, and then you have to isolate the error and figure out how to do it without rewriting half the game.
Some of them they're just not sure how to fix without telling the VGU team to handle it, because the underlying code is so faulty that there's just no reasonable way to fix it without rewriting everything in relation to it (See: Mordekaiser. His R in particular just has so many issues with every new item/champion that it's clear there's no way to actually fix it without a total rework).
Some bugs are just impossible to isolate properly and fix. Maybe they just can't reproduce it, or maybe they just can't figure out what is causing it. You can't fix something you can't pin down properly.
And some things are just too trivial, inconsequential, rare, or easily worked around to bother the time and effort to fix. Pathing at long range being weird like that is...well...I've just never seen anything even resembling it before (Edit: Looking at the vide, I have a vague idea how this would happen. It falls into 1 or 2 on my list, because it's just old sphagetti coming up again. Odds are something similar has been fixed with Anivia, or it was already patched in. We'll also probably see an issue like it with Ornn).