[jmkr]

I assume most people would find a dominant dissonant. A V7 is difficult to figure out. A V9 sounds better.

To say blues doesnt sound dissonant sounds more like only adding the relative minor b5. Or British blues rock.

[coldtea]

V7 are bog standard in blues and rock, and nowhere near hard to figure out or sounding dissonant.

And other cultures like tritones just fine, featuring them even more prominently.

There's no inherent "tritones are dissonant" human universal, it's a common practice harmony prejudice.

[zarzavat]

7 chords are dissonant. That’s why a (ii-)V7-I works. Dominant creates tension that gets resolved, or not.

But the chord function is only one third of the picture. Dominant chords can have greater or lesser tension depending on which extensions are used. A closed voicing will sound more dissonant than an open one.