I'm pretty sure Riot's designers communicate on a regular basis. You simply have to split the work and everybody sticks to their projects considering the sheer volume. That's all fine and dandy and not worth the discussion.
But it seems to become a serious problem when people work on related projects and have no clue what the others are doing, especially when the community with reading red posts 5-10 minutes a day is way better informed than their colleagues:
- The sustain nerf + jungle rework go hand in hand, yet Shurelia doesn't seem to know much detail about it. She knows the red buff is going to get changed, but no details "because it's not her project". Guinsoo just told us a few days ago that the current plan is to change it to a self-speed buff instead of an enemy slow.
- Kayle rework: Morello wasn't even aware that her new passive was changed by somebody from 20% to 10% (could have at least read the patch notes). Or him having no clue why Kayle got a base AD/AS nerf by Shurelia, but kept it anyway.
These are just two recent examples and it isn't just limited to Shurelia and Morello. It seems to be a wide-spread problem and we're hearing "no idea, I'm not working on that" more often lately.
It's kinda sad and frustrating if the players have a better idea about the bigger picture of what's going on than the people responsible for game design and balance.