In part, the story struggles to get pulses racing because Williams' rise to the top was fairly unremarkable. His was a tale of talent that grew steadily - gradually winning his audience in a sure, determined way. That trajectory is somewhat diverted by his problem drinking, but it never quite manages to truly derail it. The same could be said of the film's overall composition - capably done without taking any particular risks - it all beings to feel a bit slow and steady.
An obvious comparison would be the Johnny Cash biopic Walk The Line, but the two films are only surface similar, and perhaps the biggest difference is found in the respective profiles of their two country icons. Whilst Walk The Line was released only two years after Cash's death, at a time when his late work with Rick Rubin had reignited his public profile and made his music relevant for a new generation - Williams is long dead, better known for many as a key influencer on the folk and blues artists of the 1960s. Thus the jukebox moments in which famous songs get their first fictional airing won't stand out and grab your attention unless you're a serious fan. I Saw the Light also suffers in comparison in that it sorely lacks a lead actor with Joaquin Phoenix's capacity for brooding anger.
There is some rawness here - Hiddleston and Olsen's onscreen fights are believable if none too effective - but Hiddleston himself never quite convinces when he's required to portray a deep lying seam of darkness and depravity. His presence is always a little too winning, too winsome and assured - capable of a certain wounded sensitivity without quite tapping in to the ugly, lugubrious side of a real drunk. Likewise, Hiddleston has a handsome singing voice but one without any undercurrent of true sadness. The effect is somewhat deflating in a film largely built around a canon of sorrow.