The opportunity to play in the UEFA Champions League next season is still wide open for Barcelona, but that's how they can take advantage of every game in La Liga. There is still plenty of time to improve their performance. I'm sure they'll be able to get out of what they're going through now.
Apart from that I agree with your opinion, they are only a few points behind, it is not impossible with 1 or 2 games they can improve their position in the standings.
In general, everyone always takes into account the Champions League in a football club because it is a big event that is often inhabited by big clubs too, so it will be very painful if a football club that used to be strong but for now is not included in the realm of the Champions League even though Barcelona is also a big club in the arena of football.
Champion league is best achievement for every club and give much income when participating on this event except Barcelona as historical club have many champion league trophies. I think they have two way for participating in champion league next year, first should success finish on top four position standing in La Liga or try other way become the champion on Europe League if failed on La Liga standing top four position they still get chance for next years pass to champion league with Europe League way.