Only one can lead: guitars, voice, bass or drums. Whatever takes the lead will compel others to follow because lead means sketching out the structure of the song. The classic metal albums all lead with guitars and vocals catch up while drums provide accents and bass does whatever it feels necessary.
Repentless reverses this formula. It is built around Tom Araya’s mostly fast-spoken or chanted vocals, and guitar keeps up and drums frame the whole thing. The bass doubles the low notes and does little else, but Slayer has always used that technique. The problem is that in a desire to make catchy choruses and compelling verses, Slayer has relegated its most powerful aspect — the lead rhythm guitar — to a supporting role.
Despite a number of good riffs that call to mind material from the Seasons in the Abyss era, on this album Slayer has had to contort itself to fit around the vocals like a rock song, which de-emphasizes guitar and consequently cramps it and, in its reduced role, forces it to show off and simultaneously keep itself restrained. This keeps the worst of metal guitar and throws out the best. In addition, this reduces songs to minimal song structure based more around a lyrical narrative (or topic of a video) than development of melodies or patterns in the riffs.
This is far from a bad album. The problem is that it is the wrong sort of album. Metal escaped from rock by minimizing the human, especially vocals and feelings, to create a gritty realistic confrontation with the nihilism of existence — the knowledge that events do not depend on feelings or mythological beings, but cause and effect. Slayer expanded its audience in the 1990s to the present by being more centered on vocal hooks and foot-tapping rhythms, and does well at this, but at the expense of what made this band great.