Some form of change is coming. That's starting to look unavoidable.
I can see why Real Madrid and Barcelona want it. Same with some of the older Italian teams, as both those leagues are pretty stale. I can see why PL owners would be for it too, as they don't want any threat to their revenue.
Think for anyone with experience of the current system it'd really harm football. It'd harm all other English clubs, as you don't want to have the best teams elsewhere. You want to compete with the best.
And as a spectacle, I don't want to see for example Man United play Juventus all the time. In the CL it has the feeling of a special event due to the draw, if they'd always be playing them the appeal really falls off a cliff.
Also, it would clearly put a financial strain on being an away fan. It'd probably end up being like US sports where there is really only the home crowd plus a few stragglers.