Theory - Vision is so powerful because everyone has easy access to invisibility
When I mentioned to my friend that every champion has access to invisibility at level 1 he seemed puzzled. I explained that Brush and the Fog of War granted invisibility, and he was like, "Well, that's not really invisibility."
I wanted him to elaborate why he thought so, but the match was already underway and we had to focus.
But it's true isn't it? Everyone, every champion, every player, is effectively invisible to their opponents for the majority of the match. Not only that, but even when we can see our enemies, invisibility is much easy to come by than we give it credit for.
- Everyone has had that one opponent outplay him or her because they stepped into a brush and went invisible long enough to wait for their cooldowns or break your attack animation (forcing you to facecheck because you were out of wards).
- Everyone has had that one foe escape by putting a wall between you and themself, effectively going invisible, or cutting corners around the terrain denying you that .3s of animation you needed to cast the spell or make the attack that would kill him.
- Everyone has had that one enemy that, through whatever means, manages to escape your champion's personal field of sight - going invisible until he stumbles back into a source of allied sight.
Is it fair to say that invisibility is incredibly common, easily accessible, readily available provided certain minimum conditions are met?
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Brush is, for all intents and purposes, an AoE Akali Shroud that works for everyone with the caveat that if you step within its bounds those within are no longer invisible.
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Terrain afflicts your champion with a very specific and limited form of nearsight - blocking (think 'reducing') all allied fields of sight by its very presence.
And if that's true, what does that say about Riot's view of 'stealth'?
Isn't it misleading to call abilities and effects that make your champion invisible by a word that actually refers to a mindset and a playstyle, i.e. stealth?
Stealth: (stĕlth) n. cautious and surreptitious action or movement; the quality or characteristic of being furtive or covert.
Invisibility: (ĭn-vĭzˈə-bəl) n. not visible; out of sight; unseen; impossible to view.

All of these champions have some kind of invisibility inherent to their kit. It may manifest itself in different ways, but they can deny you vision of themselves without needing some external source like brush or terrain or being beyond your field of sight.
And every champion, provided they have the right mindset and adjust their play accordingly, can use stealth.
Thoughts?