It's a negative for the neutral, certainly. I prefer competitive games rather than teams turning up, defending and waiting for Barca/Bayern to pass them into submission and concede goals.
I'm not just saying this to be contrary - I watch a lot of Bundesliga as my flatmate loves it. We both hate watching Bayern now.
When there's no competition, fans get bored. Look at Celtic this year. Attendances have halved and they enjoy similar, if not less, domination over the league.
Pep has pretty much done the impossible, improving that Bayern team. And that in a very short time. Sure, them being even more dominant is a negative for the neutral. It was Beckenbauer's words I called bollocks, I took it as he was criticising Pep's approach and influence (not commenting on the lack of competition in the league) and I find that hard to understand.