I prefer playing RPGs to playing computer games. They're better for a whole host of reasons we don't need to detail here - because, let's face it, if you're reading this blog you probably don't need a huge amount of convincing of that. On the other hand, for certain purposes, computer games are superior: it would not be humanly possible to run Football Manager as an RPG, for instance. You need a computer, with its massive memory capacity and its processing power, to run a simulation of that complexity.
But be that as it may, RPGs are not particularly successful in being a tool to achieve fun for most people. When people want to enjoy themselves in some pastime or distract themselves from boredom they typically want the path of least resistance to that goal. This is what I meant when I said that people are generally instrumentalist in their view of games: they want fun and they want the quickest and easiest way to get that fun. The format doesn't matter, in other words - it's the outcome. Maximum fun for least effort. Downloading a game off Steam is easier than mapping a dungeon and getting 4 people round to play through it with you. Crucially, it may not be quite as much fun in the long term (actually, it almost certainly won't be), but the fun to effort ratio is much more palatable.
The same is true of other analogues. People want the path of least resistance to the music they like. The format doesn't really matter - they want the outcome of having music they like readily available. So mp3s on an iPod, or Spotify, are better than vinyl if you don't care about the format by which you're hearing your music. The same is true of books versus TV, beach holidays versus mountain climbing, etc.
Now, clearly this is only true for many people much of the time - it's never true for all people all the time. Lots of people prefer books to TV, hiking to sunbathing, vinyl to mp3s, letters to email, writing longhand to typing, and RPGs to video games. That can still be true while, in aggregate, the instrumentalist approach prevails.
For me, as somebody who prefers books to TV, hiking to sunbathing, and RPGs to video games, the format is important. I like the fact that RPGs are social, creative, and constantly create unexpected outcomes. And I also like the other elements of the format that I think are crucial - mapping, drawing things with pencils, fiddling with numbers, rolling dice otherwise randomising results. But in general the rest of the world doesn't feel that way.
To that extent, I think I agree with Mike Mearls. But where I part company is on the solution: I don't expect the world to change, and I think that trying to force RPGs to ape video games is exceedingly foolish and pointless. I don't mind that RPGs are a niche within a niche within a niche. Though I expect I would think differently if I was employed by Wizards of the Coast to design the next edition of D&D.