Except Sugimori oversees most of this.
That doesn't mean they have an art block.
It has to be a group approval. To top this off, it doesn't matter what the fans think of Mega Flygon to them. They wanted it to look good and while many of you pick at the whole "Hey this mega has little design changes why can't they make one for Flygon" it should be obvious that the reason they have trouble is that Flygon itself is too well designed for them to work with.
I think it does matter to them. I mean.. It should. About the design I will refer you to Mega Venusaur and Mega Blastoise. Do you think Venusaur and Blastoise weren't too well designed?
Garchomp has a Mega, Charizard has a mega, Absol's mega has wings.
Except there's the difference
Garchomp is flat, basic, and already "cool" looking the same goes for Charizard. All they did was spice them up to look nicer and more appealing. Have you ever seen fakemons for Mega Flygon? Have you looked at Flygon's design and thought "How do I make this look better?"
Absol may have a few small additions but it's those additions that make it look different and better. A large majority of mega pokemon were simplistic.
Flygon doesn't fit the description at all because it has a lot going on for it's design. They want it to look nice, they want it to look BETTER than Flygon did.
There's the problem right there, Flygon is probably one of the best designed Pokemon in the series in my opinion and they can't figure out how to do it. Struggling with it for too long causes art block to spread and makes them want to go back and focus on that Flygon. The only logical way around it is to take a break for a while and go back to it later. With Aarune you could tell they WANTED Mega Flygon to be a thing, and it probably hurts them way more than it hurts any of the fans.
But isn't that what makes the Mega Evolution concept cool? Your Pokemon doesn't change forever+ You don't have to use the Mega form. In addition, Who says that every Mega form looks better than the regular form? I think Altaria looks way better than its Mega form.
Art block isn't just about how many people you have working on something, especially when changing a design. Sometimes something is designed too well, and Flygon is a good example of one of them. It had the whole art team stumped on what to do. Another explanation could be that there are TOO many good designs they had and they just simply couldn't pick one or combine designs without it looking bad.
Or god forbid make 2 Mega forms right?
On another note, I absolutely WANT a Mega Flygon. I think it would be such a cool Mega Pokemon to have. If I have to wait for it to happen then I'll wait. Sugimori wouldn't say something like this if he wasn't confident in his team. Things like that article can motivate them to try harder, the best thing a fandom can do is support this, not belittle them over something so human.
I don't think anyone is trying to be mean to GF's art team but yeah we know when to support them and when to criticize them and I don't see anything wrong with this.