The psalmist is writing about those who make and worship idols. My literal translation:
Like them shall their makers become
— everyone who trusts in them!
Those who make such things for worship are as stupid, senseless, and irrational as the figures they construct. So far as any spiritual life, thought, and judgment are concerned, they are rather the images of men than rational beings. The censure is by no means too severe. Who has not found the words leaping to his lips when he has seen the idols of the Romanists? “So is every one that trusteth in them.” Those who have sunk so low as to be capable of confiding in idols have reached the extreme of folly, and are worthy of as much contempt as their detestable deities. Luther’s hard speeches were well deserved by the Papists; they must be mere dolts to worship the rotten relics which are the objects of their veneration.
The god of modern thought exceedingly resembles the deities described in this Psalm. Pantheism is wondrously akin to Polytheism, and yet differs very little from Atheism. The god manufactured by our great thinkers is a mere abstraction: he has no eternal purposes, he does not interpose on the behalf of his people, he cares but very little as to how much man sins, for he has given to the initiated “a larger hope” by which the most incorrigible are to be restored. He is what the last set of critics chooses to make him, he has said what they choose to say, and he will do what they please to prescribe. Let this creed and its devotees alone, and they will work out their own refutation, for as now their god is fashioned like themselves, they will by degrees fashion themselves like their god; and when the principles of justice, law, and order shall have all been effectually sapped we may possibly witness in some form of socialism, similar to that which is so sadly spreading in Germany, a repetition of the evils which have in former ages befallen nations which have refused the living God, and set up gods of their own.
[Spurgeon, C. H. (2009). The treasury of David, Volume 5: Psalms 111-119 (54–55). Bellingham, WA: Logos Bible Software.]