The New York City boss won three Premier League titles and four FA Cups with the Gunners, and captained them during the Invincibles season of 2003-04, but believes they are too soft to repeat that success.
The 40-year-old also aired his disappointment at a lack of former players working underneath manager Arsene Wenger at the club.
While Vieira believes that his old club play good football, he believes a lack of physical presence and personality is costing them in terms of silverware.
He said: ‘Now when I watch Arsenal, yes they play good football.
‘But I just have a feeling they are missing something – the physical presence, the personality.
‘But on the other side the team is not doing as good as it used to and you need to win football matches.
‘They’ve been disappointing, losing games they should have won.’
Viera is also disappointed at the lack of ex-Arsenal players working in academy and coaching roles at the club.
Thierry Henry had worked with the club’s youth team before Wenger offered him an ultimatum between coaching and TV work, while former captain Tony Adams let for a new role in the Chinese Super League.
Wenger’s decision to allow Mikel Arteta to become part of Pep Guardiola’s coaching set-up at Manchester City leaves only Steve Bould and Freddie Ljungberg as former players on their staff.
He added: ‘It is good for the young players who could see a Thierry Henry, a Ljungberg, a Sol Campbell or a Martin Keown who have been at the club a good few years working in the academy, or working somewhere. I think they can do it a bit more.
‘Players want to do it but do not have the opportunity. I don’t understand it.
‘The perfect example is Ajax. You see all the old players working for the club, on the field, in the office – the door is always open for them – but Arsenal don’t do it and I don’t know why.’