Probably because there's absolutely no competition involved in games like this.
I'm by no means saying Barcelona don't play great football etc or that it's their fault but it's been fucking boring for some time now IMO how they just hammer everyone. A big part of what makes sport great is the competition, the feeling that an opponent is worthy, provides a genuine test and the outcome is unpredictable. Just doesn't happen with this team. Again, I'm not saying they're not brilliant at what they do - they clearly are - I just find it a bit boring to watch.
Tin hat on.
I'm the same. Like watching a training match. Not a fan of watching Arsenal either.