No, that is definitely not the case. Barcelona's team is still good, not good enough to be among the strongest contenders for the Champions League of course, but nowhere near lower table material.
from what i see in this season all teams are weak, so barcelona at the level that this could easily be champion, i'm a fan of real madrid, so i'm talking neutrally.
sociedad is not strong, by some luck of fate they are managing to win the games, but it is clear that they are not a strong team, they are winning by pure luck
atletico is also weak
real madrid is also weak
the problem of barcelona was dismissed a player who was very good scorers and put in players who were not so good scorers, Luis Suárez and Antoine Griezmann are scoring goals in atletico