What is a term for someone who doesn't know what they haven't experienced?
You may want to use oblivious.
If you don't want negative connotations, perhaps simply describe them as unaware:
not aware or conscious; unconscious: to be unaware of any change.
Other possibilities include uninformed or incognizant.
I posted a comment rather than an answer earlier, because there are usually off-flavours when a word is shoehorned into a particular desired meaning. As OP keeps pointing out. 'Naive', I feel, does have a negative ('should know better') connotation (though the denotation need not carry that sense). 'Ignorant', though basically meaning 'not cognisant of some facts', does carry a strong connotation of 'barbaric'.
However, I'd use the term 'innocent' here - I think most people would rapidly discount the 'not guilty in the eyes of the law' sense - because a lot of the senses it carries (see reference below) overlap pretty well with OP's requirements. (In the words of a friend, 'All words are infinitely polysemous' - so you'll never find the perfect fit, with no possibility of undesired connotations - and we won't all totally agree on what those connotations are.)
in·no·cent (adj.)
- Uncorrupted by evil, malice, or wrongdoing; sinless: an innocent child.
2. a. Not guilty of a specific crime or offense; legally blameless: was innocent of all charges. b. Within, allowed by, or sanctioned by the law; lawful.
3. a. Not dangerous or harmful; innocuous: an innocent prank. b. Candid; straightforward: a child's innocent stare.
4. a. Not experienced or worldly; naive. b. Betraying or suggesting no deception or guile; artless.
5. a. Not exposed to or familiar with something specified; ignorant: American tourists wholly innocent of French. b. Unaware: She remained innocent of the complications she had caused.
6=6. Lacking, deprived, or devoid of something: a novel innocent of literary merit. [AHD]
tabula rasa
blank slate
(for the present context) the OED defines this term as follows:
an absence of preconceived ideas or predetermined goals; a clean slate:
the team did not have complete freedom and a tabula rasa from which to work
a mind not yet affected by experiences, impressions, etc.
a young mind not yet affected by experience
the mind in its hypothetical primary blank or empty state before receiving outside impressions
something existing in its original pristine state
cultural definition Something new, fresh, unmarked, or uninfluenced. Tabula rasa is Latin for “blank slate.”
Thus you could say: My mate is new to this corporate world of jealousy and hostility - he's a tabula rasa.
Example sentences from Collin's dictionary:
"But you don't start with a tabula rasa (clean slate), you have to deal with society as it is, and try to make constructive progress. TIMES, SUNDAY TIMES (2001)
It was on this tabula rasa , Picasso believed, that a new art form could originate. TIMES, SUNDAY TIMES (2002)
Porn, on the other hand, is a tabula rasa as far as greatness is concerned. Victoria Coren, Charlie Skelton ONCE MORE, WITH FEELING: HOW WE TRIED TO MAKE THE GREATEST PORN FILM EVER (2002)
With someone new, you're a tabula rasa , which has its charms for those who enjoy reinventing themselves. GLOBE AND MAIL (2003)