With all this, I don't know if you're saying anything other than what I said - that the class is stylistically similar, but not mechanically.
We are comparing things 30 years appart, of course there are mechanical differences. But, there are also similarities. The Slayer lacks daily resources to manage, it has few choices beyond what weapon to use, it's main claim to fame is hitting hard. That's very much the same as the 1e Fighter.
Exceptional Strength is different from any 4e striker mechanic; it doesn't scale, and you had to be (very) lucky to get it in any quantity.
The various 'random' ability generation methods in AD&D made getting an 18 pretty easy, really. AD&D also had weapon specialization, for yet more damage. Sure, there's decades of power inflation between them, but given how different 4e and 1e are, the Slayer and AD&D Fighter are more remarkable for their similarities than their differences.
Another key difference? At higher levels, slayers get more toys to play with.
They get 2 stances and some bigger numbers.
An AD&D Fighter gets some better to-hit numbers and hit points, and more attacks, but nothing new mechanically.
Well, he got to set himself up as a fuedal lord.
AD&D Fighters can't keep up with the Wizards & Clerics for a lot of reasons. Slayers can.
Actually there were not a lot of reasons. There was one reason: spells. Spells were starkly limited-use powers in AD&D, they were compensated for their limitations with a great deal of power, and, as levels progressed, the limitations were no longer enough to contain the sheer power casters commanded, and the game shifted to their favor. It was just a badly balanced system. The hobby was in its infancy, and that flaw was easily forgiven or overlooked. 4e (finally) learned from those mistakes, and had a system where all classes had basically the same sets of limitations* (primarily resource management) on their major abilities (powers). Essentials repeats the mistakes of prior eds by trying to balance classes with differently-limitted abilities (with or without daily powers, primarily). I'm not saying it's making those same mistakes as badly (not by a long shot), at least, not yet, but it is the same issue, in kind, if not nearly in degree.
* as an aside, another point that often gets overlooked is that, while spells were always daily, they used to have much heavier limmitations, as well. Casting a spell in AD&D meant having both hands free, being able to speak (and hear), having exactly the right material components readily at hand, standing upright on a stable surface (no, really, you couldn't even cast on horseback like Gandalf), and doing so, uninterrupted by attack, damage, or whatever, for a varying but often substantial portion of a 1-minute combat round. It was not always easy to get spells off in combat, it was virtually impossible in melee. Through editions, those limitations have been lessened, and 4e really did away with virtually all of them. Casting a spell is now no more limitted than swinging a weapon. That 'parity' I'm constantly harping on /was/ a two-way street.