Exactly - that's all I've been saying (just not as calmly as you).
Elba's not what I pictured either - but why not let ourselves, as fans, be open to a NEW interpretation? We've already had the memories of the books - those won't change - so with Elba (if he even were cast) we're getting something brand new that we've never seen.
By holding the line and refusing to accept a "new" version we don't even know if we'd like it - maybe we'd love it! Maybe Elba would be amazing, like Morgan Freeman's Red. We can't know until we're willing to try. Yeah, it could fail - it could be a total trainwreck...it's a creative risk, which can bring big rewards and epic failures.