It doesn't take as many lore contortions to explore the MW (you know, how we get to Andromeda is this big secret for some reason). Not to mention the possibility of perhaps seeing familiar locations again someday.
That's how it's better
The character of the Catalyst shouldn't change based on the choice we make. It shouldn't turn into a petulant child stamping it's feet and throwing blocks because we're not buying its lies.
To your first point, the lore contrivances are even worse. You'd need to suddenly justify the total isolation from the MW in a place where travel across the galaxy is ubiquitous and instantaneous. So you've got an even bigger issue: you're justifying a total failure of communication and travel in a galaxy where each is foundational. Now you've also got to justify how multiple technologically advanced races somehow totally escaped any kind of interaction with the MW Council races. And you've overpopulated a galaxy in a way that undercuts the Reaper premise. And that's JUST the handwave you need to even get to the Relios Cluster on the MW. That's not even getting into the usual contrivances about how anything could be set after ME3 while all the characters are totally ignorant of the events of it and the other major choices.
MEA has a single major problem: getting to Andromeda. The only other potential problem is related to timing - when do the arks leave? That requires two separate handwaves. You need way more ridiculous handwaves to make an isolated cluster in the MW work. You'd be doubling down on stupid again.
To your second point, I don't see how it's inconsistent. To the refuse crew, the Catalyst behaves the same way in all the endings - petulant child that prefers genocide to even a hint of being wrong. And to the non-refuse crowd, the Catalyst reacts appropriately to Shepard's decision to doom the galaxy to investable extinction. That multiple interpretations of the same character are possible is not per se an issue.
Now excuse me while I take a cold shower and shove my face in a vat of acid, as I cannot believe I just defended the catalyst or any part of the arble-garble that is the ME3 ending.