The fact that some Christian apologists pick up on the concept of scientism and use it for their dubious purposes doesn't mean there's no legitimate use of that concept. There is a cultural split in the academy between the sciences and the arts (although there's also some collaboration here and there, too). Each side is liable to demonize the other, especially as modern knowledge becomes more fragmented. So scientism is just a result of academic tribalism.

Einstein also questioned quantum mechanics, as do plenty of theoretical physicists, like Sabine Hossenfelder. They don't question the data, mind you, but some of the interpretations of them. No one knows what to make of the data from the famous experiments.