I haven't tried a continuous glucose monitor myself but those non-diabetics who have generally claim that it gave them interesting insights into how their blood glucose level reacted to different foodstuffs and timing of meals. There is a lot of individual variation there due to genetics, lifestyle, gut microbiome, etc. We'll probably never see a large-scale, long-term randomized controlled trial to show that CGM use improves health outcomes for non-diabetics. But for healthy people who already have the basics dialed in, a CGM can probably help them eke out some additional marginal gains.