D&D has three economies.
The first economy is the accrual of power or the ability to build a character; how a character spends resources to acquire powers and options and plusses. The first economy includes everything from the rate at which classes grant powers, picking a race that provides stat bonuses to key stats, to spending gold on equipment. This is an important economy and a robust system leads to a really enjoyable character creation and planning process.
The second economy is the spending of power or the ability to play a character; how the resources acquired are funneled and spent through the finite actions available. If you spend a move action jumping over a crevasse, fail, and spend the rest of your actions gaining your footing and climbing out of the pit, that was an economically poor round. If a feat lets you spend a surge for a +2 bonus to a d20 roll and you spend all 12 surges every combat tricking out every d20, that is an economically strong decision because you consumed more resources in the same amount of time for greater average output per action. A system that invests rules in the second economy provides a fun tactical experience where aptitude in the system is rewarded with effectiveness.
The third economy is the *player’s* experience of playing the character. This economy is more ambiguously defined through how cumbersome it is to be effective and how much time it takes. A system that requires you to rack your brain to be tactically effective is no fun if you aren’t interested in racking your brain. At the same time, if it takes you three minutes to resolve your turn and then you have to wait 15 minutes until you are up again, that might not be fun. You might prefer an economy that only gives you 30 seconds to resolve your turn if you get to go again in three minutes or feel engaged outside your turn.
What follows is a generalization across editions, but hopefully a defensible one.
It feels like Third Edition focused on improving the first economy. Third Edition provided incredible character creation options to hone in on your vision. Unfortunately, as the options ballooned, the second economy grew out of control and many builds were too effective for the game to have balance. Fourth Edition sought to improve the second economy while preserving as much of the first economy as possible. If 4e had to choose, it chose the second economy, but strived to preserve the first.
Both editions dramatically improved on the economies they sought to improve, but largely ignored the third economy. It isn’t to say that they didn’t care about it, just that it took a back seat to other priorities. I also wouldn’t argue that 2e or older editions *focused* on the third economy, but rather the games were options-light enough that the third economy sailed along healthy and strong. That speed of play made combat feel more chaotic. It made you feel like you didn’t have to make a tactically perfect decision because you’d go soon enough again. It was also a lot of fun.
I personally really enjoy the investment in the first economy that 3e introduced and cannot imagine playing without the investment in the second economy, but I miss a robust third economy. As the game has grown more complex, the third economy needs attention or it will wilt. All of the economies are crucial to the overall play experience and it is probably the product of multiplying the three economies that best describes the game. As the third economy has wilted, the overall fun (for some) has actually decreased despite the game being mechanically superior.
The good news is that if you buy this concept that the quality of the game is the product of the three economies, even modest investment in the third economy will pay tremendous dividends since the product of the first two is so great. There are a lot of ways we can invest in the third economy, some small and simple while others are bigger, more profound changes. Some we’ve already explored like the simple idea of using only two-dice and others are still to come. Hopefully they work.