OP, are you writing us from 10-20 years ago (i.e. the past)? At this point I can safely state, no, this is not the case everywhere. Your hospital sounds like it does not value case management because if it did, it would not tolerate MDs not answering your questions or responding cooperatively to you and your peers. Someone higher than us needs to show your value and your worth.
Your department leadership needs to show that a good relationship and specifically trained RNs under close supervision carrying out case management can increase the likeliness of re-imbursement, reduce length of stay, reduce readmission rates, and increase quality of care! My guess is that your department heads are not doing his/her job with taking care of you and your department. In fact, if anyone needs to be replaced based upon what you are writing, it is your department heads and supervisors.
For example, I worked in an environment where I was way more involved with discharge planning than I cared to be as a Staff RN, but that was because the case management department voluntarily gave up a lot of their job to the Staff RNs rather than show that they needed (and deserved) more staff to be effective. In any case, it effected their pay, made for poor patient outcomes, and made the role of case management useless within that organization at the time. If I were in your shoes, I would look at an outside agency, an insurance carrier, or a competitor of my current employer to seek better treatment and career fulfillment.
In the meantime, your current employer is in for a rude awakening if they take the steps you have written. Your employer, depending on their access to capital to cover poor financial decisions, will be impacted hard financially speaking and may even close in the next few years. I have seen hospitals close based upon a variety of poor financial decisions... Your organization is about to make a big one if what you are writing will come to fruition.....