Writing in 1883 about his first visit to Rome in 1840 Ruskin says:
Of Raphael, however, I found I could make nothing whatever. The only thing clearly manifest to me in his compositions was, that everybody seemed to be pointing at everybody else, and that nobody, to my notion, was worth pointing at. ( Works, 4.117).
In 1845 Ruskin referred to Raphael and Michelangelo as 'good fellows but the ruin of art' (in Shapiro, Ruskin in Italy: Letters to his parents 1845, p 97). The same point is made more formally by Ruskin in relation to Raphael's frescoes of 1509-11 in the Stanza della Segnatura in the Vatican:
And from that spot, and from that hour, the intellect and the art of Italy date their degradation... And it was brought about in great part by the very excellencies of the man who had thus marked the commencement of the decline. The perfection of execution and the beauty of feature which were attained in these works and in those of his greatest contemporaries, rendered finish of execution and beauty of form the chief objects of all artists; and henceforward execution was looked for rather than thought, and beauty rather than veracity. ( Works, 12.148)
For Ruskin, 'the medieval principles led up to Raphael, and the modern principles lead down from him." ( Works, 12.150). It follows that Ruskin distinguishes between the earlier and later work of Raphael, and the importance of the Pre-Raphaelites as looking back to the time before the fall.
'Pre-Raphaelitism has but one principle, that of absolute, uncompromising truth in all that it does' ( Works, 12.157). Only the earlier work of Raphael, before his arrival in Rome, was in that 'ancient and stern medieval manner' ( Works, 12.148). There, in Raphael, was a decisive move from the medieval to the classical, and away from 'vital' religion to 'formal' religion (see Stone of Venice I at Works, 9.31), a shift important both for Raphael and for the history of art in general.
An aspect of the decline was the attempt to improve on God's work in nature - see the reference to Shechinah, and compare Vasari on Michelangelo. In The Stones of Venice Ruskin quotes Raphael on the need to show things as nature ought to have made them rather than as it did make them - 'soleva dire Raffaello che il pittore ha obligo di fare le cose non come le fa la natura ma come ella dovrebbe fare'. Ruskin comments, 'Raffaelle was a painter of humanity, and assuredly there is something the matter with humanity, a few dovrebbe 's, more or less, wanting in it.... Raphael had something to mend in Humanity: I should have liked to have seen him mending a daisy' ( Works, 9.407).