Apart from devaluing planning and strategy pre-game, this single rift scuttler change also reduced JG decision making from "where do I want to be on the map?" to a more predictable PvE style of play. It also would most likely not be a JG vs JG fight but rather one with lane interference. Plus, the asymmetry itself would devalue adaptive strategies in the jungle such as starting the top buff for a specific level 2 gank with red buff or to path towards bot or to avoid the enemy JG etc. This is because in addition to getting a leash, the enemy jungler would also get a scuttler that I have no access to on the other side of the map. It's a bit like if a chess game started where already 2 moves are made. 1. e4 e6 and now you have to see what strategies are available. However, because the asymmetry has already been created so early, your openings on both sides are very constrained. The Sicilian isn't available. Hypermodern openings are not an option. The structure is too defined to give players the freedom to paint the mosaic how they like. You want asymmetry but it should be organic not forced because forced asymmetry just reduces flexibility and options. It makes things stale and starts to rather clearly define the meta by itself.
If I am thinking about where to start early in order to help which lane etc. (based on CC, who pushes and various other factors), the other jungler can just pick something with a safe clear and go for rift scuttler essentially every game as his strategy. He doesn't even have to think about lanes until after that because the reward is so large. Now I am put in the situation where he has a highly reliable strategy with a guaranteed strong reward and I am just HOPING that my different pathing to perhaps pressure will be rewarded. In most games, what will happen is that this reliable reward will pay off better than my mind game with creative pathing which puts me behind when unsuccessful. Now, I can take this creative pathing because if it doesn't work, I can still gain an important resource.
I thought this video made some good points too: https://youtu.be/pyg1BLHEx-8?t=8m57s
BTW: I also think playing around the scuttler shrine and knowing when to take it as a team (~don't take it at 2 minutes if you want to definitely contest Dragon and can stop enemies from doing it. Take it at 1 minute to the objective. Another example is walking along the wall to avoid the vision or jumping a wall to do so.)