Because skills that generally applies to all champs are game skills and therefore not a product of you playing syndra 500 games but a product of you playing 500 games of mid.

If you are diamond thats not because you are "so good with syndra that you have reached godlike levels of power with her that every other player on the earth who doesnt play syndra can never achieve" Its probably because you are good at the game generally and can roam gank and generally spot a mistake :)

Sure you play Syndra at your best but i am pretty sure you could switch to any other similair champ and do pretty decently fine. Likewise a guy who have played syndra for 50 games straight and is a division above you would probably also do quite fine against you in a mirror matchup.

There is a reason proplayers can pick up champs like Azir in only two weeks, despite his "insane skillcap". It did not take them 500 azirgames, but just those 50 to get used to him.

I think there is a point where your gain from mastering a champ is limited quite heavily, and that point is for the most part really early which means that if champ is suddenly rewarded for being mastered a ton of people would quickly be forced to get this champ as the relatively few games you invest in them would give huge profit back simply because some illusion of skillcap.

Ofc it must be rewarding to learn a champ and pull off awesome plays, but it should never be punishing to play champs that does not have "INSANE SKILLCAPU"

Imagine a scenario, Riot decides that this new champ "Mox" should be 20% better than every other champ in the game when you can pull of that quite hard QWEQRQW combo.

Bjergsen plays Mox for 14 games and learned the QWEQRQW combo, now bjergsen got a champ that is 20% better than every other champ thus being op. Is it fair that bjergsen is getting #1 simply because he can QWEQRQW and then overcome every obstacle ever, effectively rendering the annieplayer who played perhaps 30 games of annie useless? IMO its not, perhaps im wrong.