The 50 countries already have a deal with the EU, the EU does not have to negotiate with them. Once we Brexit it is the UK and UK alone which will have to negotiate 50 new trade deals as well as those often mentioned others with the rest of the world.
With CETA we must not forget that it falls way short of the level of access to the single market the UK currently enjoys as a member of the EU – particularly in services and financial services. It does not and never did call for the free movement of people, but then it does not allow Canada free access to all parts of the EU economy - it is a trade deal. It works heavily in favour of the EU and it was never intended for Canada to become part of the EU lite like Switzerland, so nobody is lying.
The only reason it is ever brought up by the Leave fraternity is because it could, might possibly, perhaps be a model for the EU and UK to work under once we Brexit. It is one of a number of models Leavers keep banging on about, but that is because they didn't have a plan to work to if the vote went their way. It appears that they still don't.