I've been using this at well over the recommended level for a couple of years. The angle I approached it from is that it is stated to be one of three molecules that the body uses to synthesize glutathione, a powerful antioxidant. I didn't know that it clears homocysteine which is said to be destructive to blood vessel lining. It is very easy to take as it is sweet and dissolves easily, so I take it as one of my beverage sweeteners. I'm actually drinking coffee with glycine and allulose right now (plus powdered mushroom, creatine and cinnamon)
Never seen any bad press about it and we get some naturally from food. Dr Brad is a highly credible YouTuber imo and there several others who back its use.