Because it is most likely that they got kicked out (or in fancier words "left on his own") for a reason and you don't want whatever mess he caused back at Blizzard to happen on your place.
There are people that are just incompetent on their job. Those are however easily indeintified: they make a massive mess, the lesson is learned, and the mistake will not happen again - and somewhere in between the dude is fired. Sadly, Ghostcrawler is none of those. The problem with him is that he has the completly wrong visions and goals about something that will inevitably BREAK by trying to force it to fill into those goals. It's like a political ideologist ignoring all reality for his grand project, no matter how many problems it causes. (*add "communism" joke here*)
The problem is that such a process is slow, so there's no "big bang" that will make the company just slam the breaks and correct the course. If anything, once enough energy and effort has been invested on such a "wrong route", they just keep going, because "well we already put so much into it!!!", which is the absolute opposite of it being helpful.
Now what am I talking about in specific? Not really the runes, or the preseason, it's about the general underlying philosophy. Now I remember him saying things like making this game a thing for generations, something extremly big and whatever - and already here I'd say "No. Stop. This is not how any of this works at all". While it is true that LoL is a massive part of gaming history already and surely a landmark of geek culture, that is not a basis to develop a game on - mostly because even of the best medial product people will grow tired off. Starcraft 2 is a massive part of gaming culture as well, and it was a big deal while it lasted, and now it's coming out as F2P and none cares anymore. That's just how things are - and Blizzard did the right thing that any gaming company would do: bring things to an end and do what is your job as a game dev, which is MAKING A NEW GAME, which they did with Overwatch.
But how does this affect LoL? Well, Riot as a studio is completly fixated on this ONE GAME THAT TOTALLY IS THEIR LEGACY TO THE GAMING WORLD or whatever according to Ghostcrawler. Since it is their only product aside from some random merch, they have to profit from it because a game company doesn't run of air and water. Now, that inevitably sends the focus towards the ECONOMICALLY MOST PROFITABLE PLAYER GROUPS.
And those are: Esports and New Players.
Esports is where the game celebrates itself, and where the most high sums of money flow - simply the money you could charge for ADs from sponsors must be enormous. Or the sponsors of esports teams - in South Korea there's a whole industry around it. At the same time you have a certain star-dom for your playerbase, which is also nice to have. Not much needs to be said here.
New Players lack most of the content, so they are most likely to spend the most money. Also they are not invested enough in the game to actually see any of its flaws properly yet, making them the perfect cashcow to milk.
Note that both groups are ABSOLUTE MINORITIES WHEN COMPARED TO THE NORMAL PLAYERBASE. Yet, all design goes towards those two groups, and it all boils together when suddenly the game gets designed around the idea, how fun it is to WATCH ESPORTS FROM A NEWBIE PERSPECTIVE.
The thing is tho: a video game is something you PLAY, not something you primarely WATCH. So gearing a game towards watchability is obviously pressing against the core principles that made it a good game to begin with. Faster matches, more damage, RANDOM THINGS FLYING AROUND AND GO BOOM!! Who gives a shit about immobile champs? No one, they are not funny to watch or make big plays. Even trades? No, we want people to go for the 1vs5 sole-hero narrative and GET AWAY WITH IT, because that is more "exciting".
No one at Riot cares about the millions and millions of people who a) don't watch esports and b) aren't easily fascinated newbies who are potential whales ("big spenders"). They don't even give a shit about the "old whales" either - those have no more money to spend after all, and if then only for the occasional new skin. Not comparable to the amount of money a new one could spend.
And in the position Riot is in now, they are forced to keep on that because they are economically dependant on their one single game they have.
You know what they SHOULD have done? Used the fact that they have build a recognicable brand and popular characters to expand with new titles. Used the lore as a springboard for new games and then distributed then over their already existing audience for cheap. Like, imagine they made something like a nice and neat metroidvania platformer about Ezreal exploring the world or some other nonsense, and then sold it for RP over the client, maybe for 10 or 15 bucks. Given the million-strong audience combined with a relatively low development cost, they would have raked in MILLIONS in profit, while at the same time they would have expanded on the story, which in turn would have opened up more options. Not to mention the whole universe they'd could have established in modern geek culture...
But in this case they wouldn't be dependant on SPECIFIC MINORITY GROUPS to keep their actual big title going.
That's what a smart game studio does: producing games. And since Riot has not produced a single thing in the last years aside from a number of extra characters and a whole flood of irrelevant cosmetics, I think it is safe to say that as a gaming company right now they are an utter failure. They tied themselves to their game, sink or swim, with Ghostcrawler being the figurehead of it all.
But it will sink. That's not pessimissm or me wanting the game to die, it just a FACT. In five to ten years LoL will be "history" and new games will take the stage, as it has always been. The mere idea that you can keep a game running forever is already nonsense, the attempt to design around such a concept is already taking the first steps to making sure it dies even faster.
It's kinda fascinating how the pattern repeats: back then WoW was THE thing. It was the thing that would stick around forever and ever, then A CERTAIN SOMEONE build on that vision despite it going against the fundamental principles of the medium itself, and then that fucked over a lot of things did a lot of damage.
Now we have a game that is seemingly THE BIG THING THAT'S GOING TO BE AROUND FORVER, and yet again there is a certain someone, WHO'S ACTUALLY THE VERY SAME PERSON, who does the exactly same thing which again fucks over a lot of things because of the very same reasons he fucked up things before.
Games are not meant to last forever. No form of media does. Sure, some become classics, but even those are barely watched. It's something people as a mass maybe have seen once, or something academics talk about at times, but nothing they binge on regulary. So the very notion of pushing a design on that way is going against all reason, and can only end in disaster.
Ya should have focussed on lore, because stories and their protagonists go on over generations. But game design? Not so much. So maybe give Ghostcrawler a slap and teach him his place, before he does not only bring the game down, but also the wonderful potential all the lore around it has.