Since when? Historically, they aren't on our level. United were careless and complacent last year, underestimating their opponents, and as a result failed to qualify. As for City, losing out to a hungry and motivated Napoli, in addition to the always dangerous Bayern Munich in their maiden season is no shame. However, this season, they have been embarrassing, considering that they've struggled to even get points off Ajax (managing a draw in 2 encounters).
I rate Juventus as a top 8 side in Europe (we are far ahead of everyone else in Italy), and as such, elimination in the group stages would be deemed unacceptable and inexcusable.