I'd suggest there is no fallacy in Wordsworth's "The World Is Too Much With Us." I think seeing a fallacy would be a misreading. Paganism is a worship of and a respect for nature. The speaker is saying that he would rather be a pagan who communes with the "Sea" and the "winds" than be a Christian who has lost touch with nature.
He does not in any way address literally becoming a pagan or anything of the sort, and even if he does, one could not argue that that would constitute a logical fallacy. Nature is not primary in Christian beliefs, but it is in pagan.
I suppose that if you want to say Wordsworth is giving a false impression of paganism, you can say that he is giving the impression that it will help the speaker actually feel better about himself and about humanity. So the false impression is that paganism will be more spiritually rewarding than Christianity.
The fallacy involved would be in the idea that if the modern world makes you unhappy, then it follows that Christianity is at fault. The speaker seems to be saying this and thinking that he can get to be less sad if he goes back to the old ways.
I do not disagree with the first answer, but I think your question is starting with the idea that there is a fallacy. If there is a fallacy here, that is what it is, I think.
William Wordsworth, in his poem "The World is Too Much With Us," isn’t arguing, of course, for a return to pagan nature worship. Rather like Gerard Manley Hopkins’s blasting tirade in "God’s Grandeur," he is dismayed that Christians, given to business and banking, have lost sight of sea and vernal woods. They should pay less heed to the world, more to the earth. What "powers" have they laid waste? The ability to open themselves to nature’s benevolent inspirations. Modestly, the poet includes himself in the us who deserve reproof. The impatient outburst ("Great God!") is startlingly unbookish and locates the break in sense between octave and sestet in an unconventional place.