Like a teenager, their new-found technology convinced them that they knew it all. But we have matured and realize we know very little. All glazes and glasses are slowly dissolving. Stable glazes just dissolve slower. So we are aiming at a moving target, but in general, we want to achieve glazes that dissolve slow enough that we can barely detect it with sensitive instruments.
Chronic effects are difficult to recognize and even more difficult to trace.
A chronic effect of barium, for example, is high blood pressure. Since so many people have high blood pressure, it means that barium poisoning will be just about impossible to recognize. Therefore, the burden is on the manufacturer of the ware to make double sure that barium will not leach. If there is a doubt, why not emulate the barium effect using a safer oxide like CaO or SrO. Many well known pottery instructors encourage making glazes almost totally by trial and error on the material-mixing level, considering only aesthetics. They tell us to use these for non-functional purposes, but these labels are quickly lost by 'visual' people so taken by the interesting surfaces of flux and metal saturated glazes that they lose all interest in safety.