I prefer to think that they are struggling to score goals rather than not trying to score many goals in a match because looking at their condition for the beginning of this season it seems very difficult for them to score more than 2 goals in 1 match.
There still needs to be some familiarisation when trying out some of the younger players and Lewandowski's performance is still hampered by the opposition's marking which makes it difficult for Barcelona to find many goals in their matches.
Despite this the chances of them winning definitely remain as they are the favourites and the worst possibility is a draw although this would be difficult for Betis to force a draw.
I just hope Robert Lewandowski get back to his full potential like that at Bayern Munich were he could be able to score several hat tricks in one season, ever since he came to Barcelona I've not really been impressed with his performance compared to when he was at Bayern Munich, Barcelona are known to be very dominant and very high in possession on the pitch, they love to press their opponents and force them out of their defense line which is a very fine tactics that could make them easily win matches against smaller club but you'll find them pressing and failing to put the ball into the net, and it would fall back to Lewandowski inconsistency for Barcelona, since he's the top 9 it's his responsibility to get the ball into the net but it's been uneasy for him instead it's the Barcelona wingers and Midfielders that mostly scores for them.
Lewandowski has admitted that he has slow start this season because if we compared to his goal records last season is much better than now and even his goals records with Poland national team is much better than in Barcelona and Lewandowski has been complaining Xavi tactic while Barcelona only playing draw against Getafe last month this because he hasn't gets enough ball supply from the midfielder so that's why he was unable to scores at that time but i think it's only a matter of time to see Lewandowski reach to his top performance again because gradually he has found his shape again and the latest proof is he was able to scores two times in a row when Barcelona win from Osasuna and Villarreal