total absence of Riot Stashu who's supposed to stay in touch with us
Keep in mind, his communication is not a god-given right for the playerbase. He is taking it upon himself to answer questions and discuss things he feels he can offer constructive discussion on, and his most recent comment in that thread directly addresses quite a few of the concerns players had in that thread.
We already filled over 100 pages with feedback and only very few posts were replied to
Stashu is one person. The forum community is thousands. It's not surprising he only replied to a comparitive few of the posts.
Stashu constantly picks posts which seem to embrace the rework whereas negative feedback remains ignored
Feedback along the lines of "this rework is completely the wrong direction" is really difficult to address in a way that actually promotes healthy discussion. Even if it's well-written and "correct", it's very possible for there to be bias in either direction. This is especially true for recent changes before they have time to settle, because we as humans dislike change.
why shouldn't anyone else from the staff be allowed to talk about the rework with us?
It's less a matter of who is "allowed" to talk about something; it's about who is qualified to discuss it. If Stashu was the lead on this project, it makes sense that he addresses it.
If Stashu isn't going to take us serious, who will?
Really? He doesn't address a certain concern and it comes down to him not taking the community seriously? He posted on that thread 34 times, I think it's safe to say he's taking the community seriously.