Actually I don't see Barcelona not taking their Champions League game seriously. Because of the results of their last two matches because a lot of players who are usually the first choice can't play because of the injuries they have. It is very difficult for them to qualify from this group stage because they have to finish 2 matches with a win, and also the result of the Inter Milan match will be very decisive for their next step in the Champions League. It would take a lot of magic to see Barcelona qualify for the knockout phase.
Barcelona really want to go as farthest as possible in Champions League because it means they will have more income to heal their finance crisis. I don't think it is a good explanation to blame all on injuries. Opponents of Barcelona did not have their best players for their matches too and all clubs must be able to cover injured players and achieve good results for their clubs.
Inter Milan and Bayern Munich are well deserved to go next in this group. Sorry but see Barcelona next season even it is bad to not have them in Champions League after next two match days.
But Barcelona must accept the fact that their fate will be determined by the Inter Milan match so they can step into the Europa League if they don't qualify in the group stage and of course if Barcelona continues to play in the Champions League their income will increase but what can it all be in vain when see now that it is far from qualifying in the group stage.
Before that Barcelona did not perform optimally and really wasted many chances with Inter Milan but it must be known that Inter Milan are also quite good at playing so they couldn't add goals to win because Inter Milan's defenders were too strong what I saw.