2nd Edit: Because people seem to think I somehow am against a maneuver system for the martials or something like. Want to make it clear in a single line. This post's message is aimed against people that heavily criticize playtesters for disliking the original playtest, and people that for whatever reason would have like to see that first playtest as the final print. Anything that is out of this 2 points is out of the scope of this post, like for example a modern reinterpretation of the system with the current fighter, which is not something I am covering here (and actually do support).
Edit: This post is not against the idea of current base Fighters having access to maneuvers, in fact I too am in favor of it. This post is merely to explain what the original concept of the Fighter was, as many people believe it was something closer to what we currently have only with maneuvers on top, as have seen many people wish that WOTC never reworked it, when that was not what playtest Fighter was. I still would love for some optional rule to give it (and also other martials) access to maneuvers, or some other unique martial system.
There is a common thought upon hearing that the Fighter in the original 5e playtest had maneuvers that recharged each round, and that is that WOTC neutered it and the playtesters were dumb for asking for simpler stuff. I am here to (partially) defend that decision based on the original playtest and comparing it to what we eventually got in the official 5e release. Many people imagine a current 5e Fighter just with maneuvers on top, while the original playtest Fighter was anything but.
To compare, let's make the comparison on what a Fighter on this original playtest got, versus what the released 5e Fighter gets, level by level. As there were multiple playtests, some widely changed the class and the way it works, will only take the first one that released rules for the Fighter into consideration.
How Superiority Dice worked in this playtest, you get a certain number of them, with the amount and the size of the dice growing as you level up. You start with 1d6, at level 3 becomes 1d8 and at level 5 becomes 2d8 (the original playtest only went as far as level 5). All Fighters start with the maneuvers Deadly Strike (can add any number of Superiority Dice to a damage roll) and Parry (can reduce damage received equal to a roll of any number Superiority Dice), and your Fighting Style, which here works more like a pseudo subclass, gave you additional maneuvers at level 1, 3 and 5. To use them you spend one or more superiority dice depending on the maneuver, and you recharge all your dice at the start of your turns.
At level 1 both Fighters get to pick a Fighting Style, 5e Fighter then gets Second Wind, while playtest Fighter gets Superiority Dice with the Parry and Deadly Strike maneuber. Let’s imagine I want to make an archer, so in 5e I pick the Archery Fighting Style, while in playtest I pick the Sharpshooter Fighting Style. The Maneuver they obtain from it is Precise Shot, which lets them add a Superiority Dice to the attack roll if the enemy has half cover or three quarters cover, but only up to the additional AC the cover gives. Precise Shot is plain worse than Archery, as Archery is a passive buff that applies to all situations, while Precise Shot only works against creatures with cover, while not even securing it can roll high enough to bypass it.
At level 2, 5e Fighters get Action Surge, arguably one of the most powerful features for the level they get it, while playtest Fighters get nothing. Other than bonus HP, this is a dead level.
At level 3, 5e Fighters get a subclass, while playtest Fighters get one additional maneuver from their Fighting Style choice. We picked Sharpshooter as our Fighting Style so the maneuver we get is Snap Shot, which allows us so when we make any action other than attacking, we can make one ranged attack as part of the action, with the only drawback being that the damage of the attack gets reduced to a roll of the expended Superiority Dice, with no additional modifiers. Useful but highly situational.
At level 4, 5e Fighters get a feat, while playtest Fighters once again get nothing at all.
At level 5, 5e Fighters get Extra Attack, while playtest Fighters get another maneuver from their Fighting Style. We picked Sharpshooter so the level 5 maneuver we get is Shift, which allows us to spend a Superiority Dice to move 10 feet as part of the attack action. Again, good but highly situational.
And from level 1 we can already see the biggest problem with the system. It lets you choose between a damage reduction, damage buff, or a small ability, which is far from what people nowadays think when they imagine a Fighter with base maneuvers. If you compare, this is the same system as the criticized problem with the Rogue’s Cunning Strikes, which is that they must trade damage to use a minor ability. In fact as it stands, Cunning Strike is as close as possible to the original idea of all Fighters having maneuvers.
Just for added info, in an eventual playtest that still had the Superiority Dice concept that went to level 20, Fighters don’t get action surge until level 11, and extra attack bounces from getting it at level 6, to getting it at level 5 but making you choose when you get it between making it work only on melee weapons or on ranged weapons, and in either case each attack must be made against a different creature.
So no, the original concept of the Fighter wasn’t this complex thing that dumb playtesters were unable to accept. Rather was a not well thought system, as the only decision was “Do I want to make a bit more damage, is it more worth to use this niche ability that is only useful in a handful of situations, or I save my dice to mitigate damage?”. Fighters didn’t have dozens of decisions each round as some people seem to believe original playtest Fighters did, and had potentially even less decisions past level 3 compared to nowadays as current Battle Master is way more complex than the original maneuvers system. Did it have potential? Yes, I think so, specially at higher levels in tier 4, but as is, if the original maneuver system stayed we wouldn’t have Indomitable, Second Wind, actual subclasses, or Action Surge from level 2, which bring far more decisions into play.