Well... I too, stand four-square against the dastardly
and despicable crime of sentimentality in verse (especially
as it pertains to God's noble creatures).
But ... nothing that is weak or bad about this effort of
Coleridge's (or the starting lines from Marvell) derives
from the use of rhymed couplets. To say so comes dangerously close to the notion that certain meters and/or
stanzaic schemes, etc., are mimetic and/or appropriately expressive of, only certain kinds of subject, theme, or feeling--
a doctrine I think false.
Cheers to all