They had to make it work for multiplayer. In which you can't pause. even looking up abilities in real time would get you killed. They had to do the same thing for Mass Effect.
i'm sorry, but in Mass Effect Radial spell menu exist... How do you think you can control the spells Liara use, or Mordin, or Garrus ???
How could we launch Garrus spells, or any of the companions spells without the radial spell menu...
There is an radial spell menu in Mass Effect 1/2/3...
There is a radial spell where you could switch weapons and use their spells in ME1/ME2/ME3... Didn't you remember - of course no radial menu in multiplayer but ME3 isn't a multiplayer game, it is a story game + an very good multiplayer mode ...
In ME1/2/3 AI use all the special power/capacity (spells)
DAI/ME3 Mutiplayer is another aspect of the game, in Multiplayer the tactical camera don't exist, of course, we can't pause in Multi.. do you think they should remove also the tactical camera in campaign mode because in we can't use it in Multiplayer ?
Us DRAGON AGE PLAYERS / MASS EFFECT players haven't buy Mass effect or Dragon age for the Multiplayer, us the original bioware supporter buy those games because of the story...
Of course i have played 1,5 year of more to the ME3 multiplayer, but firstly, before ME3, i had never played multiplayer games (except Vendetta online on macintosh... and may be an old Battlefield on Mac or pc can't remember, but one of the first one)...
We are story players ... This is what RPG is : A story in which we are the hero... This is what Dragon Age / Mass effect are : A story where you are the Hero... in Mass Effect we saved the entire galaxy, unified even the Geth and the quarians, pacified the Krogans, even the reapers are pacified now, and they help us instead of reaping us... the entire galaxy is one people (un seul peuple) now... 
And in Dragon Age we (the hero) unified all the nation of Thedas, Dwarves, Dalish, Elvens, Mages, templars, even the werewolves (depending your choice)...
Don't you remember the paper RPG books we had when we were tennagers ? the books where you were the hero with choice? it is the same, you read the choice possibility at your disposal, you think about it, you make your decision, and you go to page 3 or 4 or 5 depending your choice on page 1 ...
In RPG game (game where you pause to think about tactic /spell you will use) radiant menu is essential, specially on console because we don't have keyboard to map 25 spells to 25 keyboard keys...
And limiting us to 8 spells (us and the AI/IA), because they want to put a game on the market too quickly, before christmas (end of the fiscal year - and the period where people spend the more money in the year) and they have forgotten to include the code of the Radiant spell menu ...
it is a SHAME ...
This desserve our foot in their ... or an exalted march against them...
Think about it, Bioware are the Corypheus templars, we are the Circle mage and the chantry loyal templars, and since Dragon Age 3, Bioware the templars want to restrain us to only 8 spells because they fear we became a too strong mage/warrior ? Next step is push us to play Dragon Age 4 with our feets or our teeth ? or without controller ?
I mean where is the logical to restrain us to 8 spells ? Spells / capacity are for a warrior/rogue : special Move/special trick, for a mage : Magic formula they can recite... Once a warrior/rogue/mage learned those technics/magic formulas, they can execute each one of them on the battlefield...
It is not like if they had a special device specific to each move/spells and they can only have one with them at a time because this special device if too heavy... Spells are mental, warrior capacities are physic (they learned them they are definitively part of them)...