You are basically correct.

But allow me to rant, for which I apologise. Feel free to ignore, it's not that interesting, and I'm not an expert.

The main thing is (properly installed) moisture barriers, if necessary increasing ventilation, getting rid of any moisture, choosing the right insulation for the right job, etc.

Eg. rockwool is very absorbant and is even used in hydroponics, but if you pop it in an attic, use a decent moisture barrier, but ventilate it well, it's not a disaster if it gets a bit moist sometimes. Meanwhile, in an (almost always) damp basement, forget using rockwool. Even using PUR/PIR foam is likely to cause issues, even if you use the best and most professionally installed moisture barrier. Better off using XPS. Meanwhile, when it comes to wall insulation in older houses, spraying foam into the intrawall cavity(inner wall, space, outerwall), can also cause issues.

The problem is that people will hire a company with a load of good reviews. They're friendly, they're affordable, afterwards the house is nice and warm and well insulated. Everything's covered up, so even if you were an expert, it's not as if you can check if they didn't half arse their job or if they aren't well intentioned morons who installed a moisture barrier the wrong way around so it only allows moisture in rather than letting it out.. But years later, when the damage starts becoming apparent, when people start falling ill from mould, or the concrete has become so weak so you have a pothole in your living room, the company likely doesn't exist anymore. And it's not as if you can hire a company with 50 years experience, because some of these kinds of insulation are quite new, and not everyone has experience working with older houses.

Eg. Lime mortar started being being phased out at the beginning of the 20th century, so it's no surprise someone who's 'only' 40 wouldn't know it has different properties than portland cement.

And for professionals who do know their shit, do it properly, and charge accordingly, it's not unlikely the homeowner will go with the cheaper offer because they don't think it'll make a big difference but can save thousands.