Thomas Tuchel called England's support "silent" and said he could only hear Wales fans for much of the Three Lions' 3-0 win at Wembley on Thursday night.
The 7,000-strong travelling support made themselves known in the English capital even as England plundered three goals inside the opening 20 minutes, adding to the five they scored in Serbia in their last game.
There were large pockets of empty seats around the national stadium but it was those who were in attendance who bore the ire of the Three Lions boss, despite fostering such goodwill with the manner of recent performances after a shaky start in the top job.
He told ITV Sport: "We could have been 5-0 up at half-time. We couldn't score the fourth and fifth ones. The stadium was silent. We didn't get any energy back from the stands. We did everything to win.
"Yes [we expected more from the fans]. What more can you give in 20 minutes? We didn't let them escape. If you hear just Wales fans for half an hour, it's sad because the team deserved more support today."
Keane: Wales like 'lower-league side' before half-time
Wales had hoped to use the friendly at Wembley to build momentum before next Monday's World Cup qualifier against Belgium, but sloppy defending from Craig Bellamy's side allowed England to race into a 2-0 lead after 11 minutes.
Those goals from Morgan Rogers and Ollie Watkins settled England and shellshocked Wales before Bukayo Saka curled a stunning third into the top corner to put the game out of sight with just 20 minutes on the clock.
Sky Sports pundit Keane, speaking at half-time, told ITV: "It's like [Wales] are a lower league team that has gone to play a Premier League team in the FA Cup. They just can't compete."
He added: "They had a poor start and never recovered. England have dominated in every aspect. They are shellshocked."