Richarrrrdi genuinely don't know where you got the impression that optimal movement in league requires spamclicking "right in front of you as fast as you can"
it's a game with a right click to move unit control scheme
in an active fight you move your unit closer or further away from the enemy between attacks and out of a fight you just click where you want to go
literal rts controls
it's genuinely just a matter of what you're used to because to me, the more traditional action camera and controls are making it 10x more confusing for me to tell what's going on because i don't have the 360° awareness that the traditional rts isometric view and the ability to move the camera independent of your character afford you
I'm not a league player, but according to my brief research when I was looking into the game, you have more control over your character when the distances you ask them to walk are shorter, which makes sense because of pathfinding and all that, along with it just generally being efficient in terms of how you move your mouse. This seems to mostly be relevant during team fights and when you're trying to juke people. If I am wrong about this about optimal clicking distance in league thats fine. Regardless of distance though, I am certain that you do need to click a lot to be competitive, which I find straining and annoying.
As for the cons/pros of the different camera angles. I think the benefits of top down are way more apparent in an actual RTS, so thats why i have no issue with that angle in that genre.
I get your point about it being harder to have full awareness because of it being 3rd person. If good players have issues with randomly getting flanked all the time, then maybe its an issue that can be dealt with by refining the map, as its pretty complicated and theres a ton of different ways to traverse it. Maybe its like a tf2 map that has too many flank routes to watch.