I'm sure we'll see similar style games pop up soon.
Sure. But not in Blitz3D. They had a vision for a great game and they executed it perfectly.
No they didn't. TF2 has changed substantially over the years. The final game is nothing like their original vision. If you want to find a reason why TF2 happens to be a good game, blame luck, coincidence and the developers choice to stray and adapt from their vision, when they stumble upon something that works, but doesn't fit the vision.