Temperature isn't a measure of entropy, but the internal energy of a system. Internal energy is the total energy sum of kinetic and thermal and gravitational energy.

You might wonder how that's calculated, and the short answer? It isn't. We rarely look at the actual value. This also goes for enthalpy and entropy. What matters most of the time is the difference in enthalpy/entropy/energy. If you take a look at various enthalpy numbers across textbooks and software and steam tables, you'll see the value vary significantly depending on what they use as their 0 point. No matter where the scale starts though, the difference between two distinct points will remain the same.

I honestly am not sure what I made confusing. The definition I gave is the SI definition of Kelvin & Celsius since 2019. The formula I gave is more verbose than it has to be but it's what you get when you expand it.

https://www.nist.gov/si-redefinition/definitions-si-base-units