I think a lot of people end up sort of mislead by the different modes - in so many games, "free play" mode is for when you've exhausted the campaign, learned the mechanics, and just want to mess around with all options unlocked. For KSP, the campaign makes some effort at a tutorial via the mission sequence, but makes "learning to function" much harder than free play.

I like the science mode suggestion; gating off complex parts lowers the burden of choice, but without the financial pressure it's just "try this and learn to use it" rather than a race to unlock more powerful gear.