There are two issues here, does research have to be groundbreaking in order to get you a PhD, and does it have to be groundbreaking to get you a career in the academy?
I can only answer as someone in the social sciences in the US, I'm sure there are differences between fields, and countries.
A PhD dissertation doesn't have to be groundbreaking to be accepted. It needs to be original research that shows a familiarity of the existing scholarship in a field and contributes to it in a meaningful way. In doing so, it doesn't need to be revolutionary in any incredibly way, it just needs to be significant.
Of course, what makes something "state of the art" or revolutionary is often a judgment call. But, it is worth noting that the vast majority of research in any field is not revolutionary, it fills in the blanks and moves things forward a little. Academic research is like trench warfare, a war of inches with occasional breakthroughs.
You increasingly do need to have ground breaking work in order to get a career. There were 30 job openings in cultural anthropology last year, and while its hard to say how many people were applying, it could easily be 500-1,000.. Back when there were 200 positions a year, the people who did the most innovative and ground breaking work would get the top jobs. But now there is a climate of scarcity in the job market, and less prestigious colleges have a lot of candidates doing impressive work to choose from. Its a buyers market.