Answer by taking a quote from the following article:

Innervisions is the 16th studio album by American musician Stevie Wonder, released August 3, 1973, on the Tamla label for Motown Records, a landmark recording of his "classic period". The nine tracks of Innervisions encompass a wide range of themes and issues: from drug abuse in "Too High", through inequality and systemic racism in "Living for the City", to love in the ballads "All in Love Is Fair" and "Golden Lady". The album's closer, "He's Misstra Know-It-All", is a scathing attack on then-US President Richard Nixon, similar to Wonder's song a year later, "You Haven't Done Nothin'".

Although Innervisions was recorded and released before Wonder's accident, most people associated it with the musician's fast recovery. As with both Music of My Mind and Talking Book the previous year, Innervisions was received warmly by music critics. Wonder's versatile musical skills were praised by critics. Billboard published that "the liner credits Stevie with playing all the instruments on seven of the nine tunes. So in essence this is a one-man band situation and it works. His skill on drums, piano, bass, and arp are outstanding, and all the tracks work within the thematic framework." The New York Times wrote, "Stevie identifies himself as a gang and a genius, producing, composing, arranging, singing, and, on several tracks, playing all the accompanying instruments. But Stevie Wonder, you see and want to know more. At the center of his music is the sound of what is real. Vocally, he remains inventive and unafraid, he sings all the things he hears: rock, folk, and all forms of Black music. The sum total of these varying components is an awesome knowledge, consumed and then shared by an artist who is free enough to do both."  Many others also praised the variety of musical styles and themes present in the album. One reviewer from Playboy wrote, "Stevie Wonder's Innervisions is a beautiful fusion of the lyric and the didactic, telling us about the blind world that Stevie inhabits with a depth of musical insight that is awesome. It's a view that's basically optimistic, a constant search for the 'Higher Ground', but the path is full of snares: dope ('Too High'), lies ('Jesus Children of America') and the starkly rendered poison of the city ('Living for the City'). Wonder seems to say that all people delude themselves but have to be well to pay their dues and existentially accept the present. 'Today's not yesterday,/And all things have an ending' is the way he puts it in 'Visions,' the key tune of the album--pretty yet serious, harmonically vivid. There's a lot of varied music here--Latin, reggae, even a nod to Johnny Mathis ('All in Love is Fair')--but it's all Stevie, unmistakably."  Some reviewers were less enthusiastic. Jon Tiven from Circus argued that there was a lack of memorable material: "Just when Stevie had some momentum going, he went and put together a concept album of homogeneous music and rather typical lyrics. Unlike his last two albums, there are no real low spots on this album, which I suppose is an improvement, but there are no songs on Innervisions which are truly outstanding either. There's no 'Superstition,' no 'I Believe (When I Fall in Love It Will Be Forever).' By constructing a solid ground from which to work, Stevie has lowered the ceiling, and put a damper on his talents."  Musicians also showed consummate respect for the achievements of the album, with Roberta Flack saying to Newsweek that "It's the most sensitive of our decade ... it has tapped the pulse of the people."  Innervisions won Grammy Awards for Album of the Year and Best Engineered Non-Classical Recording in 1974, while "Living for the City" won the Grammy for Best R&B Song.

Why did he say that
but there are no songs on Innervisions which are truly outstanding either.