This wasn't United's fault. Whether or not he followed the RA or should have is not for us to say (he may well have seen safe visual deconfliction and I dare say we have NO idea what THEIR SOPs are--and cannot base another's decision on our frame outlook).
The bottom line I think is that we have a significant amount of crews who are unable to maintain visual separation and make visual approaches without the aid of the magic or relying on controllers to do pilots' jobs for them. I view this as a problem--the US ATC system is the most efficient in the world--bar none. It relies on a whole bunch of tricks including reduced separation AND on pilots being able to maintain visual separation and safely conduct visual approaches (as a sidenote a visual approach clearance can be issued with either the field AND/OR the preceding traffic to the field in sight). Relying on the controller as a crutch due to our lack of ability, skill, or knowledge is unacceptable in my opinion. In order to play in a particular sandbox one needs to adhere to the ROE OF that sandbox (and not the other way around). So if we buffoon things up we run a risk of being kicked out of the sandbox.
Anyone can make a mistake and any crew can make a mistake -- but when you have recurring issues is when you have a problem.