That's hardly the point though. The point is you can either choose to follow one path or another. If you're going to flip-flop or play neutrally, then you're playing as someone who hasn't got their mind set on the goal. Is it a perfect system? No. But within the confines of Mass Effect 2 world and the possible outcomes the game offers, it makes sense.
Except I honestly didn't see any kind of consistency between the Renegade options, or even the Paragon options. It's not just about the character maintaining an opinion on one particular subject, it's about what implications that opinion has on the character as a whole. The Paragon path can be anything from meekly charming to needlessly aggressive, with the only connecting factor being that it's arguably more pleasant or positive than the alternatives. Take, for instance, when you first visit Omega - you walk into the nightclub, and a few Batarians say "what're you looking at?" Your "intimidate" option, naturally, makes Shepard say something intimidating. Your "charm" option... Makes Shepard say something intimidating in a slightly more subtle manner. As opposed to asking them if they think it's a good idea to be starting a fight when the bouncers are on the other side of the door, or anything else that isn't a straight threat. Hardly what you'd describe as charming.
At no point did I get the impression that "Paragon Shepard" or "Renegade Shepard" were distinct characters that Bioware wrote - all in all, it seemed like they took each situation, decided on the three or five most likely responses the player would want to take, and assigned light side points to the one they thought was most positive, and dark side points to the one they thought was most negative. Another example of this is whenever the discussion turns to Cerberus - the Paragon option is usually the passive-aggressive, cynical option, while expressing agreement or understanding generally results in Renegade points. If there was any kind of consistency, Renegade Shepard would be even more aggressive than he usually is, and Paragon Shepard wouldn't be so snarky - but since opposing the racist terrorist group is clearly what The Good Guys would do, and reconciling with the racist terrorist group is what The Bad Guys would do, you get light side points for being petty, and dark side points for not immediately being aggressive. Bioware likes to dress these indices up in interesting words, whether it's "the Path of the Open Hand" or "Renegade", but it always devolves into "Saint" or "Asshole" when it comes to distributing the points.
(Speaking of points, while I hardly disapprove of the system Bioware appears to have used to write their dailogue trees, using the points awarded to track the persuasive ability of the character is inexplicably arbitrary, and on the first playthrough, can be fairly counter-intuitive to roleplaying - but that's another topic entirely.)
Frankly, I take greater issue with your notion of a flip-flopping character. Having a different take on a situation than the writers is hardly "indecisiveness". To a utilitarian Paragon Shepard, destroying the cure for the Krogan genophage would be perfectly in character, given that he might think that the possible risk of another war with the Krogen is too great a danger for the cure to exist yet. I simply don't understand why you think an unfaltering and unquestioning moral code is necessarily a sign of a character's determination, nor why such a thing is illustrated by sticking without fail to the Paragon or Renegade paths presented.
Eremiel said:
It is self-contradictory to be able to console and offer comfort to a close friend while disapproving when a random stranger asks you a loaded question designed to frame you in a way you don't want?
When "Renegade Shepard" has presumably treated Mordin with as many insults and disdainful comments as he possibly could - along with everyone else he's ever met in his life - yes, offering consolation all of a sudden
is self-contradictory.
Loaded questions indeed.