The warnings on the packages are not always a complete or even good picture of the real risk. There are several reasons for the differences between what is written, and what is real.
Most makers of photo developing solutions are in great legal danger if they understate the risks. Imagine if a maker didn't have any warnings at all. Any person who claims injury by a chemical can say they were not told of the danger. The lawyers would have a field day. On the other hand the makers take on no added danger if they overstate the risks. If they try to scare the heck out of people, they can say they did their best to keep people safe. So the makers are biased toward making any dangers look larger than in actuality.
MSDS data sheets are similarly biased towards not underestimating potential risks. They would be irresponsible if they did not indicate the full range of worst possible consequences arising from stupidest possible errors or worst possible accidents with materials.
There is almost no benefit to makers to indicate only the normal consequences from normal use of products. All the pressures are to effectively be as alarmist as possible.
Fortunately, with D-76 and many other well known and widely used materials, there are literally millions of people who have used D-76, for example, for many decades with almost no crises.
I do not want to imply that there are no risks at all, just that with things like D-76, you can look at a vast collective experience and see that the real risks are modest and manageable.
So that I do not present an unreal picture of D-76, I'll state that there are two risks to D-76 that should not be ignored. They are: Toxicity, if, say, you are foolhardy enough to eat the package of developer, or shake it in the air and breathe in as much as you can, etc. One component, metol, can set off an allergic reaction in some people so don't handle it more than needed. Wash up fast. Use gloves. Don't eat it, don't drink it, don't consume food or drink in the darkroom, don't scatter the powder into the air as you mix it, don't keep it where children can get at it, don't let your hands sit in D-76 for long periods and you have probably dealt very well with the toxicity risk. Environmentally, one of the developing agents in D-76 is not good for microbes in the environment. Now, though, with the wide use of digital photography, the amount of the developer being released into the environment is far smaller than a couple of decades ago. It is a consequence of our increasing knowledge of the environmental consequences of our actions, that we now see that it would be bad to continue the level of dissemination we once had.
I am arguing that we keep in mind that many if not most household cleaners are considerably more hazardous if used carelessly. Common sense is the best basis allied with some knowledge. Common table salt looks scary in it's MSDS. I'm not kidding. Sodium Chloride. MSDS sheets need to be read with their limitations in mind. Read them, but don't read them as gospel.
