Both Uses of

sufficient

in

Crediting Poetry, by Seamus Heaney

So, partly as a result of having internalized these attitudes through growing up with them, and partly as a result of growing a skin to protect myself against them, I went for years half-avoiding and half —resisting the opulence and extensiveness of poets as different as Wallace Stevens and Rainer Maria Rilke; crediting insufficiently the crystalline inwardness of Emily Dickinson, all those forked lightnings and fissures of association; and missing the visionary strangeness of Eliot.†

insufficiently = inadequately (in a manner that does not provide enough)

standard prefix: The prefix "in-" in insufficiently means not and reverses the meaning of sufficiently. This is the same pattern you see in words like invisible, incomplete, and insecure.

Attending insufficiently to the diamond absolutes, among which must be counted the sufficiency of that which is absolutely imagined.†
*

Definition:

adequate (enough -- often without being more than is needed)