I suspect some effort on the devs' part to make sure we are all playing the same speed. I can't prove it, but fast pacing is certainly pretty slow. 

The tech speed option is currently disabled. You can test this by starting a game and checking how long it will take to research the first tech without a city. (It should be 25 turns). Then adjust the setting to 'fast' and see how long it will take (also 25 turns).

Personally I think the magic tech tree could use some reworking. It is far too easy to research enough to acquire a force of 5 or 6 heroes and stomp the map together, while researching the military line require multiple technologies of increasing costs. Pacing needs to be increased, but the opportunity cost between adventuring tech versus war tech requires some rebalancing.

Agreed, its too slow. I've finished multiple games and have yet to reach the end of even one tree without pinning an AI in the corner and simply letting turns pass.

I play on large maps, and I can explore the entire map before reaching even halfway through the tree.

Yes.

Agree that it is too slow.