We know it sounds Romantic, and we know it sounds biblical now and then. But at the same time, "And death shall have no dominion" also sounds pretty modern with those slant rhymes that refuse to be put in perfect boxes. Although it's lyrical in a way sure to meet the approval of Blake and Keats, it's also got it's own spin that reminds us it was written in the 20th century.
We've got some alliteration in "death" and "dominion" that keeps the refrain sounding catchy and memorable. Later on we have some more in line 8 with that L sound in "lovers," "lost," and "love," which helps to accent that love is mighty important—just in case you hadn't figured it out already.. And those slant rhymes like the ones we see in lines 1-3 ("dominion/one/moon") and lines 13-14 ("way/break") utilize those ending consonant and vowel sounds in a less singsong kind of way. We catch the rhyme but it's not like it comes at us like a sledgehammer, which makes it sound more modern than Romantic.
And since we've got that omniscient speaker, we also get the feeling that Thomas's poem is not exactly light reading. We know things are going to get heavy and cosmic and we know we're expected to consider some rather serious ideas about life and death. So although we don't have to worry about death being the end of it all, the poem certainly doesn't sound like a day at the beach. If anything, it sounds a bit nostalgic of those beach days and other beautiful things about nature and life that "dead men naked" will have to do without.