There was no "space magic" in the ending.
There is. Otherwise please explain to me how touching two metal rods that seem to melt your face away makes one able to control or become an AI overlord.
Or how jumping into a 'bottomless pit' while being disintegrated by some form of energy beam takes ones 'essence' and allows 'synthetics to understand organics' while simultaneously 'integrating' both somehow.
And please on a level similar to 'runnig electrical current through element zero creates a mass effect field that manipulates matter'.
There is absolutely nothing pointing to those 'space magic' endings in the whole trilogy before.
IF there was an intended deeper meaning, it was lost completely by the representation of those, which are stated and shown to be instantaneous.
>>The kid[...]<<
I'm not sure why you bring the kid up at this point.
>>you were looking for something called the Catalyst throughout the entire game.<<
A device, not a character. I believe I already said that this change is pretty significant, imo.
>>Nothing is made invalid by the ending<<
Over 3 game we are basically beaten over the head with implied or spoken statements like:
ME1-3: "Genocide is bad. Something that preserved galactic peace is bad because maybe looks a bit like genocide"
Ending: "Oh, you want to kill all synths. Great! Surely you want to kill all of those others too?!"
ME1-3: "Diversity! People and species are different. But they can live together and actually do some big stuff if they work together. Chaotic, but great"
Ending: "Nope, diversity is bad. You all have to become one. Order is a must. We are the Borg"
ME1-3: "Only maniacs and politicians (aka maniacs) favour control"
Ending: "Use this and together we can rule the galaxy!"
And just to mention my favourite parts of the other rubbish the AI stated:
"There is no conflict"
While the Reaper in the background destroys an Alliance cruiser...
"We preserve the essence of advanced species, so they don't get annihilated by AI"
Meanwhile their AI warships annihilate the population of whole worlds.
I didn't see nor hear of any 'essence preserving' or ship building actions on the batarian, turian, asari or vorcha (home) worlds.
And the Best:
"We leave those species not far enough advanced alone"
Right. Tell that e.g., to the bronze age civilisation of Aphras. Oh right, the reapers bombarded all settlements on that planet, there is nothing living left, except for some single celled organisms.