There is 2 forgotten brothers of the jump duo. Sentry Rocket Jumping (using alt-fire with a wrangler, closely related to a rocket jump) And the Flare Jump (firing and detonating a detonator flare gun at the same time, not sending you that far)
When you get *really* good at sticky jumping, it becomes way more versatile. But it takes a lot more practice to get that good and it's only really practical with the sticky jumper.
Luckily that still leaves demoman with a grenade launcher, while soldier with the rocket jumper has only a shotgun. If only demo had a market gardener...