Steve Clarke's men were ripped to shreds by Julian Nagelsmann's outfit at the Allianz Arena in Group A, where the Germans recorded the biggest-ever opening victory of the men's European Championships.
Two 21-year-olds in Florian Wirtz and Jamal Musiala propelled Germany into a two-goal advantage inside the opening 20 minutes, before Ryan Porteous gave away a penalty and was deservedly sent off for a shocking tackle on Ilkay Gundogan.
Kai Havertz coolly converted from the spot against the 10 men of Scotland, who fell 4-0 down midway through the second half to a Niclas Fullkrug rocket before Antonio Rudiger's own goal gave the Tartan Army something to cheer.
However, the Scots' reprieve was incredibly short-lived, as Emre Can - who had only been called up to the Germany squad the night before as a replacement for the ill Aleksandar Pavlovic - curled home the hosts' fifth from the edge of the area.
Robertson hails Scotland for 'digging in' despite record loss
While Germany were rightfully lauded for their free-flowing attacking play, Scotland were caught cold and out of shape on numerous occasions, but Robertson was able to reflect on some positives from the second period.
"First half, we just got it all wrong really, didn't show up, weren't aggressive enough, and we let good players get on the ball. Second half, we're down to 10 men and I thought lads dug in really well," the Liverpool man told ITV Sport.
"We're so well backed over here, today was hugely disappointing. We have to bounce back quickly because there was lots wrong here and it's a quick turnaround now. Maybe it's a reminder of how tough this tournament is.
"Their big players showed up and were excellent all over the park and had an answer for pretty much everything we had. I don't think we've played to our maximum. We have to dust ourselves down and go again."
However, former Republic of Ireland skipper Keane strongly refuted the suggestion that Scotland came into the opening tie with a proper "game plan", highlighting their lack of an aggressive nature and angrily dismissing Robertson's post-game comments as "rubbish".
"It's all well and good having a plan, he said then 'We weren't aggressive enough'. You have to be aggressive in a game of football. Being up against opposition who are much stronger than you, being aggressive is part of a footballer," Keane said.
"I love watching skilful players, absolutely love it and the talent we saw from the German players tonight was great to watch. But my goodness, when you are playing football at this level, you've got to hit people. Hit them properly, hit them aggressively and do it in the right way.
"If you step off against them like Scotland did tonight... and it's no good talking after the game saying 'We had a game plan'... it's rubbish! Andy Robertson, it's all just rubbish coming out. You knew before the game what was at stake and after the game it's no good going, 'We'll regroup and we'll be angry tomorrow.'
"No, you should be angry for a long time. We spoke before the game about creating history. They are creating history all right... by playing as bad as that and letting their manager and supporters down. The tackle for the penalty and sending off wasn't aggressive that was madness, of course. Being aggressive is part of the game but they didn't lay a glove on them."
Despite Keane's scathing assessment, Scotland head coach Clarke largely echoed Robertson's sentiment, imploring the Tartan Army to "keep the faith" after his side became the victims of the biggest-ever opening Euros defeat.
The Scots have until June 19 to recover from their humbling defeat, as they meet Switzerland in Cologne on June 19 in their second Group A contest, which Porteous will be suspended for.