Lawless Darkness does sound more accessible than Rabid Death's Curse, not that it makes much difference in my book, but anyway. Of course, Watain has developed a more commmercial image with their new albums, the "movie" and all, but it's not like it makes them any worse. Watain is still good and quite original band, even if I like their early work best.
A lot of that is due to production though, Rabid Death's Curse really isn't inaccessible musically. Typically, the more established a band gets, the more a record label is willing to give the band, so cleaner production and more promotional options are a given. Many bands follow this path; Immortal, Satyricon, Enslaved, Gorgoroth, Burzum etc. Season of Mist can obviously provide more than Drakkar can.