It may be because the changes you are suggesting do not appeal to people. Rather than nits and critique, which require effort and means they care enough to spend time on your contribution, thundering silence is a good sign of widespread (mild) dislike of a given change (because people don't assume others won't actually like the proposal). Don't take that personally, though! Instead, take another critical look at what you are suggesting and see if it: changes too much, is too broad, doesn't adhere to the developer notes, is dangerous or insecure, is messily written, etc. Identify and address any of the issues you find. Then ask e.g. on IRC if someone could give their opinion on the concept itself.