Lay Hindus and lay ब्राह्मण's might be largely non-sectarian
But religious life of Hindus is alive mainly because of the great sectarian traditions
E.g. In TN, almost all temples are run by "sectarians" - be it आदिशैव's, गुरुक्कळ्'s, श्रीवैष्णव's
Lay स्मार्तs visit them

स्मार्त's are not into running / governing temple worship in a big way. At least not in southern India where sectarians rule!
The great Agamic traditions are kept alive by sectarians.
But for sectarians, these great traditions won't be alive and vibrant as they are to this day

My personal take is that Hinduism would likely have gone the way of the European paganisms and died out, in the absence of the great sectarian traditions
The sectarian traditions kept the popular religion vibrant, and the religious institutions vibrant during the middle ages

While popular rhetoric emphasizes the role of आदि शङ्कर as the great unifier / consolidator of H-doctrine, it underplays the enormous influence of sectarian thought in keeping the religion going on the ground, and in "sanskritizing" millions