During the four decades that I’ve been involved in the North American hydronics industry, there have been significant improvements in the thermal efficiency of hydronic heat sources.
The 1960s vintage ranch house I grew up in is a good example. When built, it was fitted with a baseboard-heating system supplied by an oil-fired steel fire-tube boiler. The boiler was equipped with a tankless coil for domestic water heating. A Honeywell “round” thermostat controlled the entire 1,500-square-foot house as a single zone.