Riot what happened to immobile mages?

I seriously wonder about the thought processes here. Immobile mages seem to get nothing but nerfs despite there immobility. When one is hard to play against because he can kill you really quickly you nerf him. this would make sense except for the fact that mobile mages do the same or more damage and generally see buffs not nerfs, not that they haven't seen nerfs. Immobile mages that i love like Viktor and Velkoz and Veigar just don't hold up to a well played Ahrie in the current structure of the game. when talking about balance choices when Velkoz came out i remember the sentiment being that immobile mages because they are immobile generally get higher raw power and usually some cc, but Ahrie now has a speed dash a ult with three dashes and a charm which is better cc then anything Velkoz has combined with true damage and heals which Velkoz dos not even approach having.

This being the state of things i why should i ever play anything but Ahrie or Leblanc or Fizz? Admittedly i don't enjoy them as much but they are legitimately just better in the current game structure. And I'm not saying that there are not good players on Velkoz or other immobile mages. There are and they do some times beat Ahries and Leblancs. Obviously player skill is vastly important, but all other things being equal if the mobile mage and the immobile mage have the same damage potential the mobile mage wins.

I am also not saying riot you stink why make game so bad rage because my pet champ doesn't do what i want him to. I think over all your usage of perfect imbalance is impressive. Giving players the tool box to find ways to make our own balance is great and the way you generally handle these issues is great, but in the end i am simply tired of playing against Ahrie most games because she is legitimately the best pick and has no real downsides to chose. The problem is that mid is getting stale and the options for playing there are almost none existent.

I guess the question is if mobile champs are supposed to have to pay a toll of power to get there mobility why is it that none of them do?