Lack of openness: a browser plugin that is less stable and slower on Mac and Linux that noone else can fix except Adobe...and only if they choose to do so.
Lack of openness: a browser plugin that doesn't properly utilize cookies on non-IE browsers that noone else can fix except Adobe...and only if they choose to do so.
Lack of openness: a browser plugin that doesn't properly return HTTP status codes on OS X that noone else can fix except Adobe...and only if they choose to do so.
The SWF standards (and associated standards like RTMP) are available for free on the Adobe website. You are permitted to construct alternative implementations based on this specification. I think it meets the definition of an open standard.
Would HTML not be an open standard if the only browser we had was IE, and it was horribly buggy? No - the quality of the available implementations is irrelevant to a standards "openness".
Lack of openness: a browser plugin that is less stable and slower on Mac and Linux that noone else can fix except Adobe...and only if they choose to do so.
Lack of openness: a browser plugin that doesn't properly utilize cookies on non-IE browsers that noone else can fix except Adobe...and only if they choose to do so.
Lack of openness: a browser plugin that doesn't properly return HTTP status codes on OS X that noone else can fix except Adobe...and only if they choose to do so.