Importance and influence definitely cannot be proven. They can both be argued with evidence, but they cannot be proven. What is important varies wildly from person to person, and how things truly influence us is far from known. Oftentimes we have no idea that things are influencing us.
Even if your statement is based in theoretical analysis, that doesn't make it any less subjective. A song can have harmony, counter-point, structure, etc., but that doesn't mean that the song does any one of those things well. And deciding whether or not those aspects of a song are any good is more than a bit subjective. 12-tone music has a whole host of cool music theory concepts built into it, yet the vast majority of people hate it. Why? Because they just don't like how it sounds. Explaining the theory might make them like it more, but it might not. If these things weren't subjective, then music theorists would end up agreeing on everything, and we both know that's not true. (Schenckerian analysis, for example is still controversial.)
I've studied quite a bit of music theory, too (unfortunately it wasn't offered as a major at my school), and precisely as a result of that studying, I've come to appreciate that very little of what makes music good is quantifiable. There are a whole host of things that can be quantified that can make music more or less complex, but what makes the music good or not is how it all comes together, which is completely subjective. If it weren't, scientists could just create the perfect song and be done with it.
There are plenty of artists that have made albums that I think meet all the criteria for what you've said makes MBDTF so perfect (ones by The Smashing Pumpkins, Imogen Heap, Rush, and Alice In Chains off the top of my head), but you might not agree with me about any of them, and that's a good thing. So yes, I still think it's ludicrous to claim that "No one makes albums like that," as if that's a provable fact.
You make a good point about the distinction between change vs the specifics of the change (talking about clothes). Kanye doesn't exist in a vaccuum, though. His reactions are just as much a product of the society he lives in as anyone else's. Who's to say that, if he hadn't dressed the way he had, someone else wouldn't have? I just don't think there is any way to prove that kind of stuff.
What is important and influential to the industry is provable. Album sales, fan base size, similar sounds, those are all quantifiable. It doesn't matter what's important to you personally. When over a dozen of the highest grossing musicians in the industry link the genesis of their signature sounds and subject matter to one album, that's influence, and that's irrefutable.
I can't take anything else you're saying seriously, though. You obviously don't know what you're talking about. Theory isn't subjective. Saying that albums aren't organized the way MBDTF is not a subjective statement. If you don't understand what that means, even after having it spelled out, then you obviously learned nothing in your theory courses. What I'm talking about is organisation and optimization. That isn't an opinion. Those are facts. Those are based off literal numbers.
Saying statements like "12-tone music has a whole host of cool music theory concepts built into it" makes that lack of theoretical understanding abundantly clear. 99% of modern music has "a whole host of cool music theory concepts built onto it." That's like saying baseball has a "whole host of cool physics concepts built into it."
What makes music good is quantifiable. Theory is literally the analytical study of explaining why we like music. Theory has nothing to do with being simple or complex. It's the explanation of the organization of sound frequency and their relationship with each other. Theory is "how it all comes together." There are "scientists" who "create the perfect song." They are called popular musicians, and the "perfect songs" are the millions of popular hit songs. There isn't just one perfect song just like there isn't just one perfect equasion. These people make hundreds of millions of dollars creating sounds that are crafted to be pleasing, and any basic harmonic reduction can tell you exactly why. That's theory.
I guarantee you they haven't because you clearly have no understanding of what that statement meant judging by your response. It is a provable fact. It either is, or it isn't. That's theory. This isn't a statement of "well MBDTF sounds pretty to me." It's an efficient, organized, optimized album, to the degree of which none have come close to replicating in all the thousands of albums I've listened to. That's backed up by harmonic and reductive analysis. This is math. Does that mean there can't be another as tight? Of course not, but that's the point. There hasn't been. At least none that have even come remotely close to having the exposure, and therefore influence, that MBDTF has had.
Who's to say someone else would have? It doesn't matter. They didn't. He did. It doesn't matter if someone else would have done it eventually. It doesn't matter if someone else did it first. That's what influence is. Him specifically doing it is what striggered that change. It doesn't matter if he's a product of his time. Obviously he is. Obviously his style is a product of his own influencers. Obviously his music is a product of his own influencers. 808s didn't come out of his ass. That sound came from his effection for synthpop and electropop artists of the 80s like Phil Collins, Gary Numan, TJ Swan, and Boy George. But they don't matter unless you're a music hystorian who cares about that stuff. They didn't have the platform he did when he dropped 808s, so they didn't gain the magnetude of exposure that he did with 808s. Drake is one of the biggest musicians of the 2010s. He's probably a more popular musician than Kanye right now. Is he as important or influential as Kanye though? Of course not. Drake didn't make the wave, he rode it. Kanye was a tsunami.
All this "it's just an opinion" stuff is moot. It's like saying that you can't say Elvis Presley, Frank Sinatra, The Beetles, Michael Jackson, and Queen weren't the most important and influential musicians of the 20th century because "I personally liked Greenday better, so they were more important and influential musicians to me." That's cute, but that's not what this is about.