WotC owns the rights to everything that matters in order to publish new Blackmoor material.
Older settings are often seen as generic because everything that came later borrowed their main features from them. I think it would be possible to make them feel distinct again, but I would do it through art, layout and presentation.
But fantasy has evolved today into something very different than fantasy was in 1970. That is something that could be leaned into in order to highlight those features. Or you could also lean into the concept of "Feudal Knights uncover crashed spaceship while under attack by Vikings". In any case, if you want to make it awesome, you can.