What reason is there to pick an immobile Bruiser over a mobile one that does everything better?
Why should I pick Olaf to ignore the enemies CC and dive when Vi can do it better in point and click?
Why should I pick Darius to snowball my lane and crush my lane opponent when Riven and Gnar do that better AND have a better teamfight?
Why pick Garen to disrupt/tank when Shyvana can do it better WHILE dealing more damage?
Moblity doesn't mean blinks and dashes only, high move speed buffs work as well in Shyvanas case.
These are few problems with this game, there is no reason to pick the immobile Bruisers when you can just easily pick the more mobile ones who do their job completely better in every way except for maybe ONE OR TWO things, but those don't amount to the 10 other things they are outclassed.