I would also think like you. I think Barcelona's current concentration is in the UCL league competition because there they have the opportunity to get a trophy this season even though it is tough but Barcelona can fight hard without depending on other teams to lose. It is very different from Laliga, even though they are focused and wipe out all the remaining matches, Barcelona still will not be able to win Laliga if Real Madrid continues to be consistent and it is unlikely that Real Madrid will make mistakes that will cause them to lose eight points. Maybe Xavi is aware of this, in the end concentrating on La Liga will be in vain, but for Barcelona who is in second place is still a priority. Moreover, currently Girona has lost concentration and has lost points several times, this makes it easier for Barcelona to maintain second place in Laliga.
If you look at it the other way around, other clubs have the same opportunity. Barcelona cannot come from nowhere and want to win the trophy some people are far better than Barcelona currently. Barcelona even has more chances of winning than Barcelona. No matter how serious they think they can get now, there is no way that Barcelona can win the UCL. I know they can put in more effort, but this season is not theirs because they struggled, especially in La Liga. They just started catching up recently and it is already late. There are only a select few teams who stand a chance of winning the UCL since the competition is more competitive and everyone wants to win, meaning that winning requires a lot of work on the part of the teams. Even Madrid is beginning to lose faith in them.