Some are and some aren't. For example, a "rule of thumb" for fans is: flow is proportional to the cube-root of power. The volumetric flow rate is equal to the area times the average velocity. The pressure drop is often proportional the velocity squared. The power is equal to the pressure times the volumetric flow rate, which is proportional to the cube of the velocity; therefore, the flow rate (or mean velocity) is roughly proportional to the cube-root of the power. This will not change with technology. Conversely, rules of thumb that might apply to a thermocouple may not apply to an RTD, which is a different type of device and typically more accurate. RTDs are becoming more common in industrial applications, while thermocouples are becoming less common. The answer to your question is, " It depends."

Rules of thumb or heuristics will always be useful since they are quick and do not need many resources to apply.