I’ve only seen it in pictures, but I’m not a fan either. Looks completely secular, might as well be a concert hall or something. Maybe that’s the point, throw an as wide net as possible to appeal to everyone to try to justify the cost.
Gaudi himself was deeply religious; this wasn't just the church commissioning a famous architect for the sake of it or anything. It was very much a labour of love for him, AIUI.
Also I’m not sure if it’s really Gaudí’s work, for example how the altar is way forward is an innovation from the 1970s.
The two temples and all the subsequent churches from the time of Solomon up to and including the nineteenth century may have looked radically different in terms of architectural style, but what they had in common is that they were unambiguously constructed for offering propitiatory sacrifices to God.
Churches built after that are instead built for offering a meal to mortal humans. If that’s not a secular activity, then it’s one of a completely different religion. In fact the transformation of the twentieth century was a far more radical change than the one going from the old to the new covenant, in that it has rejected both of them.
Of course like all the other new age hippie nonsense that came from that century it will eventually fall out of fashion, just like Arianism eventually did despite the Church apparently being completely overcome with it. The question is just how long it will take.
It’s possible, even likely, that the pictures don’t do it justice, so I will take a look in person at some point, but I don’t have high hopes.
Like the Mezquita in Córdoba, it's hard to get a sense of how intensely all the combined elements make an impression just from photographs.