Because of my belief in the importance of alignment, this is a question I have actually spent quite a bit of time thinking about, and I feel like I am getting closer to an answer. And as always, the more I refine the answer, the more nuanced it gets. The main thrust of the answer is that asking the question of whether there is such a thing as a perfect version of an asana, that asking this question itself is taking you off the path, is derailing the deepening of your practice.

It is simply not a particularly helpful question. To ask that question is to give preference to goals over process, and that in itself is redirecting you away from awareness and towards attention, away from the here and now and towards a pie in the sky. What matters is not whether or not perfection can be achieved (it can’t), but whether you can maintain a focus on the process of improving each pose, each breath, each movement, each moment, by imbuing it with greater awareness, more serenity, and more spaciousness, freedom, and grace. What matters is whether you can do this, improving the process, making each moment more vivid, without the need to believe that you are on your way towards perfection, without needing to believe in the existence of perfection itself.

When we feel like we have reached perfection, all we have reached is an impasse along the path, the most powerful impasse of all towards continuing along the path. After all, if we can convince ourselves that we have reached the end of the path, then continuing along it is utterly nonsensical. But enlightenment itself, the supposedly ultimate goal, is in the most essential way NOT the reaching of a goal, but the reaching of the understanding that there are no goals. Enlightenment is reaching the understanding that the secret lies in the process itself, and that whenever you have come to a greater understanding of the answers to your questions, it is time to ask the questions again, with greater nuance, with greater subtlety, so that your answers can become more nuanced and more profound each time you go through the process of asking them. Enlightenment is maintaining this process of asking the right questions over and over again, each time coming to a more nuanced, not a more definitive answer, and to continue that process indefinitely.

What does this philosophical detour contribute to the question about asana and alignment? It tells you that improving your alignment, bringing more awareness to alignment, feeling how subtle changes in your alignment change the feeling of a pose, is exceedingly worthwhile. It is one way to move along the path, to be engaged in the inquiry that is yoga. Just because there is no perfect version of each pose, does not mean that each version of each pose is equally ‘good’, equally useful. Despite there being no perfect version, coming into a version of a pose that moves you away from the path of least resistance, moves you away from a detached, non-aware practice of the pose towards a more involved, more alive, more spacious version of the pose, is a worthwhile change, means you are moving in the right direction.

Try it now: Come into a pose in which you feel that aligning yourself is challenging. Downward dog, Triangle, and Warrior 1 or 2 are all poses I find very useful for this exercise, because they are easy enough to be maintained for a while, while offering sizable alignment challenges for most people. Set a spacious, solid foundation for your chosen pose, come into the pose and notice how you feel. Start playing with the alignment, starting with the alignment of the hips (assuming your foundation is already solid). If you find that you can’t adjust your hips to make yourself feel more spacious without overstepping your edge, then you first need to back out of the pose to reduce intensity (move your bottom hand higher in Triangle, lift your armpits away from the floor in Downward Dog). You need to back out of the pose because aligning your hips more neutrally always increases the stretch intensity of the pose, giving you back the intensity you lost when you placed your hand higher on your shin in Triangle.

As you subtly change the position of your hips, notice how those changes in the hip alignment ripple throughout your whole body. Notice how those changes make you feel, not whether some teacher has told you that this adjustment is correct, and that one is incorrect. Really feel the effects of each adjustment, both in terms of the intensity of the pose, but at the same time in terms of the sense of spaciousness and freedom you experience in the pose.

Notice that an increase in spaciousness and freedom is generally accompanied by an increase in stretch intensity. That is so because when you make an adjustment that increases spaciousness, you generally are able to do so only when you stop avoiding stretching the parts of your body that you always avoid stretching. In general, we avoid stretching the hips (and to a lesser degree, the shoulders) and we compensate for this lack of movement in the hips (and shoulders) by increasing the movement along the spine, either over-rounding or over-arching the spine, or both (along different segments of the spine), depending on the pose. However, our sense of spaciousness is largely dependent on the shape of the spine, and the closer to neutral the shape of the spine, the more spacious we feel, and the easier it is to maintain a sense of serenity in each pose. That is because our sense of serenity is challenged when we cannot breathe, and moving towards a more neutral spine frees the breath.

When you start exploring the alignment in a pose, you are moving away from the path of least resistance, you are leaving the rut in the road that has been formed by your habits of imbalance, you stop avoiding the work of yoga. And that only happens when you are really immersed in the moment, truly feeling what each moment brings, rather than feeling frustrated that you haven’t achieved the “perfect” version of the pose yet. Or worse, feeling smug because you think you have achieved the perfect pose and you can turn on the auto-pilot because there is no more work to be done. :)

Bringing awareness to your alignment and playing with it is one way to deepen your yoga, to keep moving along the path, especially if you can keep refining your alignment without needing to believe that perfect alignment exists. Instead of using external markers to decide how close your alignment is getting to perfection, redirect yourself away from a goal-oriented mindset and start feeling how small changes in alignment change the feeling of each pose, increasing or diminishing your sense of spaciousness, freedom, balance, presence in the moment, and sense of serenity. That is where it’s at, not in the illusory goal of working towards perfection. And then in the next moment, and the moment after that, you get to do it all over again.

PS: So you don’t want a wishy-washy philosophical detour in lieu of an answer? If I claim that not all versions of a pose are equally valid, what makes one version better than another? The answer is simple: More spaciousness, generated with the least possible amount of effort and struggle. And how do you get more spacious? By moving your spine towards its natural double-S curve whenever possible, and when it isn’t possible (such as in deep forward- or backbends), distributing the movement of the spine as evenly along the entire spine as possible, again because that maximizes spaciousness (and reduces the chance of injury).
Which of the three versions of Downward Dog shown here is most spacious, most balanced, most free? Most people will have no problem agreeing on the same pose without needing to analyze the photos in detail. The most spacious pose is the one in the middle, the one with the most neutral spine. It also happens to be the most challenging, and at the same time, interestingly, not the one that is most gratifying to the ego. It is the most challenging because you are not simply reaching for a goal (Must. Get. The. Head. To. The. Floor!), but instead, you are moving ever deeper into spaciousness, which takes you ever deeper into the moment, and deeper into serenity.