Absolutely agree.
The first places I start investing in “energy efficiency” on a home are the doors. There are far too many homes with far too much leakage around doors.
Next are the windows.
Those two areas are the worst offenders in heat loss, because many people don’t take the time to really do doors and window installation correctly.
Next area is insulation.
Some of the best engineering ideas I’ve seen recently on homebuilding have to do with a) going to 6” walls and b) staggering studs on the inside/outside walls, so there is no direct connection from the outside wall to the inside wall through the stud except possibly in corners. This radically reduces the heat transmission of a house from the inside walls to the outside.
Right on target.
Windows and doors and lots of insulation are the biggest bang for the buck.