It's certainly true that the show is past it's best, even Clarkson a while ago said there are more episodes behind them than ahead. Personally I wish they'd say something like there are going to be 2 more series - and that'll be that.

Yes the scripting is an issue, as they try to do ever more outrageous stunts. Much better when they set out to do something, and whatever happens, happens, instead of generating scripted mishaps and the like.