Goodness, as a concept, can be a little confusing to deal with. To be "good" – what does that even mean, anyway? You can be good at something, good to someone, but good in general? It's a mystery. In "London, 1802," Wordsworth laments the lack of goodness – one might even say, he laments the badness – of his fellow countrymen. When he addresses this matter, "goodness" gets wrapped up not only in the morality of individual people, but in the overall success of the nation. On the individual level, he takes a look at the example of John Milton, whose greatness as a poet was rivaled only by his greatness as a human being – suggesting to readers that perhaps the better we are as people, the better we'll be at everything.
Morality is clearly tied to success in this poem, whether it be the glory of a nation, or the individual success of a poet.