Great reviews in the music press make a very small difference to sales (perhaps around 20,000) and adverts account for virtually nothing. When did you last buy an album because you saw a poster advertising it? Your Arsenal was Morrissey's second most critically acclaimed album yet sold in tiny quantities (even by his standards). And interviews hardly make any difference either. Have you ever bought an album because you heard the singer being interviewed?
Radio airplay is really the only significant factor. The first 3 of Morrissey's 21st century albums had big airplay singles at the time (FOTG, You Have Killed Me, and Paris).
World Peace 's only proper single, Istanbul received hardly any (languishing on the Radio 2 C-list).
And he's not too old for radio at all. Radio 2 (The UK's biggest station), XfM, Absolute etc will all happily play new music by people of his generation. James just enjoyed their highest chart position for 20 years thanks to Radio 2 sticking their single on the A-list.