It’s a bad deal because Brexit is a bad idea. Once you decide Brexit is what you want, this is the kind of exit deal you end up with. Also, too, shooting down a deal is easy; I note that all the people carping about this one are deadly silent when it comes to offering up any tangible alternative, one which the EU could possible accept.
The EU will not give any non-member a better relationship than the EU members get; and they will certainly not give such a better deal to a departing member.
Given that, the UK on exit will either be like Norway (transition period) or it will be like any WTA country, albeit one with very few direct agreements in place with anyone (no transition period or hard Brexit).
Given time, the UK could be like Canada, but that’s about the best you can hope for if Norway is a non-starter. And that agreement will take years. So, if you’re a Brexiter, what do you hope to get from an exit agreement that is better than what May has delivered? That’s the question.