I agree with you, Barcelona won the last season La liga beating even stronger team's like Real Madrid to top the league, which was a good performance and to keep to that trends, there is a need to further ride on the record and performance better than the last season, but truly this season, Barcelona have not really shown any level pf consistency in their performance and in the last few matches, it has become clear that the club is struggling in this season much more than the last season when their we're able to win the league title.
Most of the time, is either they play draw game or even lose to their opponents in this season.
That is a fact that cannot be denied Barcelona condition is no better than last season the main reason is Lewandowski the player seems to have lost his ability this season, we remember his contribution to Barcelona was very significant but this season he can't do much, but to face Napoli I don't think it's a big problem because Napoli is also in the same situation inconsistent in some matches. If we compare overall Barcelona looks better than Napoli and Barcelona should be able to qualify for round 8 apart from that, I don't think Napoli is able to compete in the Champions League we can see their history in the last season when they are at their best they still cannot compete so what do we expect from Napoli this season with worse conditions, that's why I say Barcelona is better even without Lewandowski. Whether it's a coincidence or not, I think Barcelona is lucky because their opponent is Napoli.
Apart from Barcelona, there are also several teams that can be said to be lucky because they faced weaker opponents for example Manchester City, Real Madrid, PSG, Arsenal and Dortmund while Inter Milan and Bayern Munich had to fight hard to beat their opponents. Anyway, so far we can see which teams have the potential to qualify for round 8 we already have 6 teams and have to wait for 2 more teams between Inter Milan and Atletico Madrid and Lazio vs Bayern Munich. Special for Munich, they usually always qualify for the next round at least in the semi-finals.