It's true that heat pumps have different performance characteristics from furnaces, but they weren't touching that issue, just insulation.
Will insulation reduce your needs? Yes. If you get into a situation where your foundation is responsible for most of your heat loss in -10F weather, you're in a great situation!
If improving the insulation on your walls is too hard, well that's disappointing, but that's a different topic from what happens when you do have good insulation.
Unfortunately, it's not just apt install insulation (wouldn't that be nice?), its a multifaceted problem involving energy sources (especially if you're shutting one down), heating infrastructure, housing stock retrofits, money, and more money.
The whole story about my house was just to try illustrating the difficulty of reducing a problem to "add insulation" and the downsides of ripping out otherwise-working infrastructure.
Adding insulation has complications, but not as many as you're making it out to have. You're making it sound like adding insulation requires replacing your heating system, and it definitely doesn't.
Making it just "add insulation" doesn't reduce the problem to trivial levels, but it does reduce the problem significantly.
Will insulation reduce your needs? Yes. If you get into a situation where your foundation is responsible for most of your heat loss in -10F weather, you're in a great situation!
If improving the insulation on your walls is too hard, well that's disappointing, but that's a different topic from what happens when you do have good insulation.