We need a bit more of the context to follow this passage. Going back a few lines we find that “no more so strange” is the delayed complement of the verb “appear”:
the gorgeous dyes,
The space, the splendour of the draperies,
The roof of awful richness, nectarous cheer,
Beautiful slaves, and Lamia’s self, appear,
Now, when the wine has done its rosy deed,
And every soul from human trammels freed,
No more so strange
The effect of wine, the poet says, is not (as many would have it) to inspire us with wonders, but to make the strange familiar, to reduce even these enchantments of Lamia’s palace to ordinary decorations. The delayed reveal of the complement heightens the effect of this contrast:
Not until this point does the insecure grammar itself recognize the error of equating inebriation with creative seeing. Drunkenness does not make visions appear, it makes already present wonders appear less wonderful. Alcohol numbs and, in imaginative terms, belittles, razing even “Elysian shades” to the level of the mundane. These drunken revellers are, however, the perfect audience for the desperate self-display of Lamia’s pastoral charade, her cheap auctioning-off of poetry’s wonders.
Garrett Stewart (1976). ‘Lamia and the Language of Metamorphosis’. Studies in Romanticism 15:1, page 29.
In “Elysian shades” we need these meanings:
Elysium, n. 1. The supposed state or abode of the blessed after death in Greek mythology.†
shade, n. II.6.a. A disembodied spirit, an inhabitant of Hades (= Latin umbra); chiefly with allusion to pagan mythology.
Oxford English Dictionary.
† In some accounts opposed to Tartarus, where the wicked are punished.
The “Elysian shades” are thus the spirits of legendary heroes who now reside in Elysium. In the Odyssey, Proteus says to Menelaus:
“As for your own end, Menelaus, you shall not die in Argos, but the gods will take you to the Elysian plain, which is at the ends of the world. There fair-haired Rhadamanthus reigns, and men lead an easier life than any where else in the world, for in Elysium there falls not rain, nor hail, nor snow, but Oceanus breathes ever with a West wind that sings softly from the sea, and gives fresh life to all men. This will happen to you because you have married Helen, and are Jove’s son-in-law.”
Homer. Odyssey 4.561–569. Translated by Samuel Butler (1900). Perseus Digital Library.
So in Lamia, the poet means that our attitude to these heroes, who should properly be “too fair, too divine”, is diminished by drunkenness. In this line “too” is used in the sense “exceedingly, very”, not “in excess; overmuch”.
