If the TFTA functions properly, it will be a free trade area, not a common market and certainly nothing approaching what the EU is.
The trouble is not all the players involved function properly themselves.
COMESA still has certain tariffs within it, while inside the EAC (arguably the most integrated of the blocs) there are still issues between Kenya and Tanzania on things like share ownership. And South Africa tends to dominate SADC.
But that's not to say that this tripartite agreement is a waste of time. Free trade from Cape to Cairo has been a goal since colonial times (Cecil Rhodes talked about it) and this agreement is a baby step towards that.