Robertson got the better of Maguire at the Barbican Centre in York yesterday, winning 6-2 to deny the 32-year-old a place in the semi-finals.
Maguire, who had beaten fellow Scot John Higgins 6-3 in the fourth round, knew he would have to improve when he faced Robertson in the last eight.
But Maguire - who was once the Australian's most feared opponent on the tour - could not muster enough to overcome Robertson as they shook hands at the conclusion.
"I think Neil has beaten me the last - I'm actually scared to think about it - maybe the last seven or eight times," he said. "I used to own his a*** years ago. I think I was 9-0 up on him in matches and it has happened with a few of them, like Ding [Junhui]. Neil has definitely improved - everybody knows that.
"I was just outplayed basically - no excuses there. In the first frame I missed one red and I didn't see another shot basically until I was 3-0 and 50-odd down. He kept me cold.
"The best guy won on the day. When I was sat in my seat I just felt as though I was totally outplayed. He never missed - he just played a good match of snooker."
Robertson dominated the early exchanges at the Barbican, racing into a 4-0 lead before Maguire, the final Scotsman left in the draw, got on the board in the fifth frame.
The world No.1 responded with a break of 128 to move within one frame of the match and, after Maguire pinched the seventh, he completed the job.
But, despite the disappointment of missing out on a spot in the last four, Maguire was able to look back on the UK Championship and feel as though Scottish snooker has plenty to be excited about.
"Scottish snooker is in good hands just now," he said. "We're just kind of waiting on [Anthony] McGill powering through. He is due a massive result and the other boys are starting to kick in as well."