"Finite-field" is the operative phrase in that sentence. I wouldn't tell you to use IES, as in the thing where you do g^xy mod p. I would tell you to use libsodium's box, which is a specific implementation of something sorta like ECIES, though.

The confusion is that IES/ElGamal sometimes means a family of systems and sometimes someone literally means FFDH + AESCTR or something. The abstract concept is fine, but you should use a hardened implementation.