Facebook is fine for what it is. If you don't want to see inane or banal rubbish, block the "friends" that post it, just ignore it or unfriend those that really get on your wick, provided you can cope with any potential fallout of doing so. I prefer to just ignore it, but my view of some friends has undoubtedly been coloured by their use of Facebook.
Facebook can be pretty much whatever you want it to be. However, as an alternative to forums, I find that it's horrible. If Facebook does eventually kill off forums, it'll be down to the ever increasing numbers of people that live their life on it. Most of the angling related stuff on FB leaves me cold. Too many dafties talking cobblers in text speak for my liking. I tend to follow some angling companies, waters etc for information updates, special offers, latest nes and the like. The only angling related group I have any real involvement with is the secret group for a syndicate. Only syndicate members can view it and it has proven to be quite useful for members to keep in touch and up to date with catch reports. It has even seen the odd member sign up to Facebook just to use it.
Forums may not be perfect, but in comparison they are largely populated by relative subject matter experts and rabid intellectuals. I suspect that's one of the biggest problems with forums, they are generally dominated by a relative few with either a lot of knowledge/experience or a lot of self confidence. They can be quite intimidating for those that are a little shy, newcomers and youngsters.