Is smell a bad way of determining whether meat is still good?

It is absolutely untrue and very dangerous to think that "if it looks OK, and smells OK, it must be OK." If that were the case, food poisoning would be very rare.

Food that we can sense is spoiled rarely causes illness. For one thing what you don't eat can't hurt you, and people generally won't eat food that looks or smells spoiled. But less obviously, much of what causes spoilage that we can taste, see or smell is actually fairly harmless to humans. Spoilage and rancidity are terms that are often used interchangeably, but rancidity is actually a specific kind of spoilage, caused by the relatively harmless oxidation of fats which is unrelated to any kind of bacteria or other microorganism. It's just a function of time, temperature, oxygen, and light. Fancy dried cured meats get a fair amount of their special flavor from controlled rancidity. Molds and yeasts cause food to spoil, but are also used in controlled ways to create flavor. Dairy cultures are bacteria, and bacteria plays a major role in fermentation.

What causes illness and death are usually things that we can't taste, see, or smell. Salmonella, E. coli and C. botulinum are often undetectable by our senses. Mishandled food that has been heated to temperatures far hotter than is necessary to kill any and all dangerous organisms can still kill if those organisms have produced chemical toxins or deadly spores. We often can't sense those either.

That's why the rules exist. It is critically important to take care to keep food out of the dreaded "danger zone". Foods that are considered unsafe unless cooked to a specific temperature ARE unsafe unless cooked to that temperature (although government recommendations in that matter are often overly conservative, there is room there for assessing your own risk). Preserved foods must have appropriate acid, salinity, sugar or other tested preservatives. Stored foods must be kept at the proper temperature. Dried foods must be dried correctly. Canning procedures rules seem overly strict. They are not. Learn the rules, disobey them at your peril.

There is a lot of good information here under the food-safety tag. We are not making this stuff up. The CDC "estimates that each year roughly 1 in 6 Americans (or 48 million people) get sick, 128,000 are hospitalized, and 3,000 die of foodborne diseases." That's just in the US where food handlers (home and professional) are mostly educated in basic food hygiene and just about everyone has access to a refrigerator. The worldwide figures are staggering.