Not true. You just explained what the Fahrenheit scale is based on, so clearly not “nothing”. Fahrenheit’s zero was the coldest he could achieve using available materials and techniques at the time and is a good choice: other workers would be able to achieve the same temperature, using his method, and this would aid communication among scientists working in different parts of the world. It was a good start.

But let’s not get distracted by details of early development which seem quaint to us today. The importance of having an instrument that could put a numerical quantity to the quality of “hot” and “not so hot” was “paradigm-shifting”, as the biz-book writers today call every management fad that comes along. It became possible to realize that heat and temperature were not the same thing. This led to classical thermodynamics and later to modern statistical mechanics. Recognizing the value of a thermometer, and inventing one that would work, was ground-breaking.

The “metric” system is based on the metre, but only for length. The original definition of the metre is no less arbitrary than the length of King Henry II’s nose to fingertip to define the yard. The important thing is that everyone agree on the length of a yard or a metre, whether by royal edict or revolutionary terror. The decimal nature of metric length is a convenience for school children who no longer have to memorize how many inches in a furlong. But note that only in length (and area-volume) do we use powers of 10. For time we still use seconds, minutes, hours, etc. in all but the most rigorous scientific work. And for temperature we don’t use powers of 10, either. So for both time and temperature there is no fundamental reason to use one scale over another. The freezing point of water is every bit as arbitrary as Fahrenheit’s NH4Cl brine. And temperature today is calibrated with the triple point of water, not the ice point, because the latter varies with pressure.

So there is no inherent reason to prefer Celsius degrees over Fahrenheit, particularly for ordinary use. As Tom says, 0 to 100 degrees covers the ordinary temperature range encountered by humans in the productive regions of the world. Outside that range it is a challenge to survive, much less thrive and generate tradeable wealth.