Obviously we'll never know who the Canucks might have picked had they kept their 2021 first rounder (9th overall) or their 2020 first rounder (21st overall)
But the two guys picked in those spots (Dylan Guenther) and (Shakir Mukhamadullin) by the Coyotes and Devils are probably at least a couple of years away from even helping those teams. And if the Canucks had picked either one, it would be at least 2-3 years before either guy cracked the NHL lineup, and maybe longer.
When the Canucks drafted kids like Horvat, Virtanen, Hughes, Pettersson and Boeser, they were a team with a lineup full of declining veterans. So there were immediate openings. Conversely, there really aren't any 'immediate openings' on this current edition of the Canucks.
Guenther is a winger and Mukhamadullin a d-man. So while they might have beefed up the prospect pool a bit, they'd do nothing to help Benning save his job for the upcoming season, or the season after that.