Wirtz's move from Bayer Leverkusen has been questioned by Germany coach Julian Nagelsmann this week.
But McAteer told the Liverpool Echo: "I think Wirtz has found it difficult at Liverpool.
"He was a fantastic talent at Leverkusen, part of that team under Xabi Alonso. And it was a team really that I felt Xabi built around him in the end. He was the focal point and grew into that role and responsibility. He flourished and his German career has taken off, he's a bit of a golden boy in Germany.
"He's had to move away from his family, adapt to a different culture. People forget about these things when foreign players come to the Premier League.
"It does take time to forge relationships, it does take time to create an understanding with your fellow team-mates. But also, in the Premier League there's a big spotlight on top players. Everybody has an opinion, everybody scrutinises their performance and you don't really seem to be given an opportunity to settle.
"It's like you have to hit the ground running. It's like because they paid £120m and he's a superstar, he's not allowed to play badly.
"Unfortunately it's not turned out that way. The scrutiny, the criticism, it seems to be affecting him. So I understand why he's not in the team.
"But I thoroughly think, in time, he'd be one of the best players in the Premier League."