The efficient market hypothesis has been dogma for about half a century, but there's a lot of academic research showing that value and various other factors outperform anyway. There are all sorts of structural and psychological reasons they might persist; e.g. a short-term bias among fund managers, who tend to lose investors if they underperform a few quarters.
The research does say that value doesn't work quite as well as it did decades ago.
There is no reliable evidence that value investing still outperforms the market on a risk-adjusted basis. Everyone knows the trick now so the trick no longer works.
There's no reliable evidence that it doesn't, either. Value has never been something that works all the time. You have to put up with lagging performance when growth stocks are ascendent, which could be a reason that value keeps working in the long term. Time will tell whether it has its day again.
The research does say that value doesn't work quite as well as it did decades ago.