I'm pretty sure we do indeed have different playstyles (I'm very much a "don't worry about mechanics, let's tell the story and just futz with any mechanics that get in the way with that as we go"... moreso than advancing quickly being my "thing")... but my opinions on the potential audience for Mike's high-level work I don't see it being as a result of my playstyle really. It's more just observing how the game of D&D has progressed over the last several decades. Despite the game being made that allows for high-level play (Level 20 for 3E and 5E, Level 30 for 4E)... most tables don't seem to embrace it and have never seemed to embrace it. And that is evident based on all the efforts (or lack thereof) people and companies have made to make high-level play a thing.
People use the phrase 'chicken and the egg scenario' to describe the situation (people don't play high-level games because companies do not make product for it, and companies don't make product for it because no one plays it)... but that phrase is really just describing the reality. And we can tell just based upon how few high-level products get made. Because if any company actually saw any of those high-level products of theirs actually sell... they'd make more, because they'd have an audience for it. But if they don't, then they aren't going to. And if more players want high-level material... then they should be buying as much of it that they can that is available... this isn't a situation where they can afford to be picky and choosey. If more people really want WotC to make more high-level adventures, they should have bought Vecna: Eve of Ruin regardless of how they might have felt about it-- just to prove to WotC there indeed is a market for books like that. But based on the fact that that book hasn't blown the doors off of sales records tells us both that not enough players actually care/want high-level material... and that those that do want it have very specific needs which this book did not serve.
And I don't think what I'm suggesting is all that odd or shocking. High-level games come about usually after quite a long amount of campaign playtime, and thus have very specific narrative directions they find themselves in. And thus high-level product have an exceedingly tight window to make their product being the one that would prove useful. And if it's not useful... then no one will buy it. Thus the circle continues.
To be honest... I do not think it is game complexity that makes people not want to run and play high-level games... it is narrative complexity. The story situations that DMs and players find themselves in after X amount of time (weeks, months, years) having played through levels 1 through 12 make the opportunity to continue their stories harder to continue because of whatever whackado areas and situations the characters now find themselves in. And those situations are so whackado and specific to what this party has done that you NEED a DM who is willing to create the further scenarios and stories that work for where that party now finds themselves in. Because the odds of some other company having created a high-level product that actually fits in to the situation the party finds themselves is so long that those companies realize it's probably a waste of their time and money to try.