I think your arguement is kind of silly. Kid's schedules are bloated? With what though? Is it actually valuable? Maybe if they're bloated we should... get rid of the bloat and add in things that would actually help them.

Also, you aren't teaching them what will be useful in a home in 30 years. You are teaching them what will be useful NOW. When they go to college, or get an apartment in a few years. If we didn't teach people things that changed we wouldn't teach SCIENCE! But we do. Because when you have a baseline and things change you can update what you know over time.

On top of that, your argument is self defeating. You are similtaneously saying kids are too busy for a class on this stuff but also saying they should just teach it to themselves in their free time. If they're so busy when do you expect them to do that? The entire point of a class is so that we can MAKE TIME for them to learn this stuff.

I think a furnace would refer to forced hot-air heat, with the furnace being the thing that heats the air being blown around through the vents.

Boiler would be to heat water/steam for radiant heat.

I am wondering what other appliances would be covered. What about electrical work or plumbing? Even if you don't do the work yourself, knowing a bit about what's involved can help avoid getting ripped off.

I'm regularly shocked by people who are incapable of doing basic home repairs.

I'd say anything that is relatively common and could potentially be dangerous if not maintained properly. You don't need them to be masters of every appliance. Just to be aware of the dangers of the most common ones.