In plain words
Those without clear discernment, delighting in the letter of the Vedas and declaring that nothing else exists, speak flowery words, Partha.
Word for word
This flowery speech which the undiscerning proclaim, delighting in the words of the Veda, O son of Pṛthā, asserting 'there is nothing else'...
The commentators
Bhagavadgītābhāṣyam
येषां व्यवसायात्मिका बुद्धिर्नास्ति ते —
याम् इमां वक्ष्यमाणां पुष्पितां पुष्पित इव वृक्षः शोभमानां श्रूयमाणरमणीयां वाचं वाक्यलक्षणां प्रवदन्ति । के ? अविपश्चितः अमेधसः अविवेकिन इत्यर्थः । वेदवादरताः बह्वर्थवादफलसाधनप्रकाशकेषु वेदवाक्येषु रताः हे पार्थ, न अन्यत् स्वर्गपश्वादिफलसाधनेभ्यः कर्मभ्यः अस्ति इति एवं वादिनः वदनशीलाः ॥ ४२ ॥
In plain words
Those in whom there is no intellect made of resolve — they —
This speech — the one about to be quoted — is flowery, like a tree in full bloom: dazzling to look at, delightful to hear. And it is exactly this kind of speech that certain people proclaim. Who are they? The 'unwise', Śaṅkara says — meaning simply the unintelligent, those who cannot discriminate. They 'delight in the statements of the Veda' — meaning they delight in precisely those Vedic sentences that spell out various means to various rewards, Pārtha — insisting that nothing exists beyond the ritual actions that lead to heaven, cattle, and the like. That is what they keep saying, and saying it has become their whole habit of speech.
Close to the Sanskrit
Those of whom a resolve-natured intellect does not exist — they —
That speech — this one about to be described — flowery, like a tree in bloom, shining, delightful to hear, [this] speech, characterized by [such] sentences, they proclaim. Who? 'The non-wise' [means] the unintelligent, the undiscriminating — such is the meaning. 'Delighting in the statements of the Veda' [means] delighting in the Vedic sentences that reveal the various means to various fruits — O Pārtha — [saying]: 'there is nothing else besides the actions that are the means to fruits such as heaven, cattle, and so on' — thus speaking, [they are] of the habit of saying so.