JS ended up being a compiler target anyway. Stack-based PostScript would have been fine for that and given the web a 15-year head start towards real applications and designs.
Of course Berners-Lee was familiar with DPS, since it was the display layer on NeXTSTEP and the original WWW was a NeXT app. The problem for Display PostScript was always Adobe's expensive and restrictive licensing policy. Worse but free beats sophisticated but proprietary.
(See also Sun NeWS, https://en.wikipedia.org/wiki/NeWS which suffered the same licensing fate)