It extended coverage to millions who were without. it made huge strides in many ways, including no limits on costs, forcing Insurance Companies to 15 profit margins and several others.l like pre-existing conditions. It was an important first step. Anyone had to know the Repubs would try to kill it. Obama could not take insurance companies out of the equation for obvious political reasons.
There were numerous exemptions regarding profit limits. A lot of the most oligopolistic and monopolistic markets for insurance were allowed whatever margins they wanted. The main reason for said exemptions didn't come from Republicans. It came from "Blue Dog" Democrats who had insurance connections. Max Baucus was one of them.
As you said, Republicans were going to vote against it no matter what, so this is why the negotiating was done with corporatist Democrats.
Another often overlooked factor was that many people chose not to have insurance. Not everyone wants to deal with insurance, and some people are able to use the few cash-only doctors out there -- or ones that are able to make their own payment plans. A lot of people signed up for insurance solely to avoid fines, not because they wanted insurance.