I'll give now my point about it, in my last PSL match I faced a Golem lead (surprise surprise) and I had no meganium (my team wasn't made to last but to get ride of my opponent fast) but I lead crobat with giga drain, sacked it and made sure golem didn't come back again pursuit trapping it, this was in this battle, but everytime I think about building something and I don't want to use meganium there are only strategies like those that can take care of golem, yeah sure you can lead cacturne but that doesn't mean it can come back again and keep punishing for not having a reliable wall to its attacks, so I feel there are ways to deal with it, but it's too centralizing right now, there's no way you can build a team without plugging meganium in your team or having to trapping it so it can't come back again and make you feel miserable for not using meganium.
Claydol is excellent against Golem but if your opponent doesn't have one is such a dead weight, which is not the case with meganium that it has some utility besides walling Golem.