Being a "good" singer, meaning able to hit and hold pitches, not too nasal, not given to episodes of on-stage grunting, keening, yowling etc., puts one squarely in the category of being an ordinary singer, while the grunters, keeners and yowlers at least draw attention. When Madonna came out, she could sing on-tune, but almost entirely unadorned, almost like chanting, she sang like a moderately talented 10-year-old girl. And now, thirty years on, after racking up millions (billions?) and having all that time, money and opportunity to take some breath-control lessons, learn some jazz inflections, study her "art": yet, she stills sings exactly like a moderately talented 10-year-old girl.
Umm, duh, her exceedingly-carefully-chosen AUDIENCE was... 10-year-old girls. It's the Ronald McDonald approach, get 'em while they're tykes, and you'll earn forever... It worked for Frank Sinatra and the bobby-soxers, though they were more like a mature 13 years old. The thing is, it only takes a few years and 13 (or 10)-year-old girls grow up to be 16 and become a very high point of interest to, say, 16-year-old boys. Do you think there was ever a single solitary 17-year-old boy who bought a Madonna CD because he liked it? Yiminy.
I have a friend (female) who resolutely refuses to read Pattie Boyd's and Eric Clapton's autobiographies, because they say mean things about George Harrison. Apparently in between long episodes of Hinduesque asceticism (and celibacy re: Pattie) he had to take vacations involving scotch, cocaine and groupies. And as most serious fans refuse to know, the Beatles honed their talents from 1960 to 1962 playing in G.I. strip clubs in Hamburg, subsiding on booze and every kind of pill imaginable, at one point actually living in a whorehouse who's residents adopted them as pets. And then they moved back to England, grew out the moptops, and quite consciously adopted characters: the Smart One, the Quiet One, the Cute One, the Doofus. And began writing songs for 10-year-old girls like "Love Me Do", "Please Please Me", "I Want to Hold Your WHAT?", etc.
Tho point is: these people were extremely talented at what they did, far more than you or I (duh), but what they did was really marginally related to being, or becoming, a "good" "singer."