A lot of it looks like you are saying because Medicare is not prefect, ACA has some serious problems. I agree that the ACA has problems and is not what I hoped for, but some of what you write seems exaggeration to me. A quick reading gave me these 2 things. I need to read the rest to see what else is wrong, or inaccurate.
First "seniors are not allowed to partake of the exchanges". While technically true, they already get medicare and the ACA is provide insurance to people who don't have insurance and the exchanges are for those who do not have insurance coverage. Rather like people who have insurance through work don't use the exchanges. The exchanges are for people without existing insurance coverage through Medicare or work. Technically true but meaningless.
Then the pre-existing thing, I thought Medigap was supposed to cover that. Also this thing from Medicare Advantage says you can get pre-existing coverage except for ESRD.
http://www.medicare.gov/find-a-plan/staticpages/learn/rights-and-protections.aspx
http://www.medicare.gov/sign-up-change-plans/medicare-health-plans/medicare-advantage-plans/things-to-know-medicare-advantage-plans.html
Finally this article saysthere is no pre-existing Medicare issue.
http://voices.yahoo.com/medicare-pre-existing-conditions-preauthorization-5337127.html
Where does Medicare come into this, and is there Medicare health insurance for preexisting conditions? The short answer is that In Medicare, there are no preexisting conditions. Medicare is the Federal health insurance program originally passed into law in 1965 to provide coverage for Citizens and legal residents age 65 or over. Later the law was modified to allow coverage for disabled individuals under 65, and for people with End Stage Renal Disease (ESRD). Once in the Medicare program, you are covered for any past or present medical or health condition. Prior to Medicare you may have suffered from preexisting condition coverage exclusions, but those will not and cannot apply once you enroll into Medicare.