A penalty by the hosts was the only goal of the game as the Three Lions lost 1-0 in their first Nations League game of the campaign, ending their longest ever unbeaten run.
And Ashton believes the performance was concerning, with just 170 until the World Cup in Qatar starts.
"It shows that if you think for one second that you've cracked it, then football has a habit of kicking you in the backside and showing you otherwise," he told talkSPORT.
"England are a scalp for any team, you can see that with the celebrations, but the thing that bothers me most is how lacklustre we were.
"You can say it's the end of the season, the players are tired or that it's hot, but I'm sorry that's pure excuses.
"When you're here and you're representing England, that tempo and that quality cannot be at that level.
"The first half was awful, there was nothing to get out of your seat about and I feel like I haven't seen that sort of performance for quite a while from Gareth Southgate's team, and that's what worries me because these are crucial games.
"You haven't got long until the World Cup and these games are crucial for seeing partnerships and it looked like some of the players, I mentioned Jude Bellingham in particular, he looked completely different when he had a bit of freedom.
"There's way more questions than answers when it comes to the World Cup squad."
Ashton went on to criticise a late substitution made by Southgate, when he brought on Kalvin Phillips for Conor Coady with ten minutes to play.
That's despite Tammy Abraham, who scored 27 goals for Roma last season, sitting on the bench, something which ex-striker Ashton believes is a 'dig in the ribs' for the centre-forward.
On Abraham's lack of involvement, he said: "As soon as I saw Kalvin Phillips stripped and ready to come on, I thought, 'That decision better work, because if not you're going to get pelters for this'.
"I'm staring at my screen at Tammy Abraham, I'm thinking you need a goal and you've got a striker who has been brilliant in Serie A.
"That would have been such a dig in the ribs for him sitting there watching and you don't get picked to go on. It'll hurt him in terms of his mentality.
"If you turn up from the start and don't have the right tempo and don't change things when it's clear that it wasn't working, that's the biggest worry.
"It was like turning the clock back and watching some of the dross from England pre-Gareth Southgate."