First, “My religion doesn’t prioritize attendance” is sort of a cop out: all religions prioritize people showing up for the things they do together.

If you think it’s a cop out, then try and compare the data to a nation that’s religiously mixed. Lebanon might work.

But, I think you’re overstating. If you’re Catholic, failure to attend church is considered a sin you need to confess. If you’re Orthodox, it’s not a sin, but it’s heavily frowned upon. If you’re traditional Protestant, it’s just a missed opportunity. And if you’re evangelical, nobody is likely to even notice, unless it;s a smallish rural church.

If you’re Muslim, the mosque is open for prayer seven days a week. You’ll get a few people who duck in for prayer, but most do it in-place. There’s nothing special about a Friday, other than the fact that the noonish prayer will get you a lecture as well.

Point here is that religions, and denominations within religions, all place different emphases on holy day attendance, and levy different levels of accountability on their members. All those affect holy day attendance to a greater or lesser extent, making comparisons somewhat problematic.

Another interesting study might be to compare religious attendance to religious identification across denominations and religious. I’d wager (well, if I wagered, which I don’t) that you’d find that the ratio of religious attendance to religious identification is significantly higher for Christians than it is for Muslims. And it would be risky to make assumptions about relative piety from those numbers, I’d add.