/snip
In AD&D (either 2e or post Unearthed Arcana 1e) assuming Str of 17 you only have +1 to hit and damage and 3 attacks/2 rounds, rising to 2 attacks/round at level 7. A longsword therefore does 1d8+3 damage or an average of 7.5/attack (9.5 vs large) for an average of 11.25 dpr. But this is extremely frontloaded as other than getting a magic +1 or +2 sword the next damage increase the fighter gets is the level 7 2 attacks/round and more likelihood of facing large foes.
By contrast in 5e a first level fighter with Str 16, longsword, and the duelist fighting style is doing 1d8+5 damage for 9.5 damage/attack or in round terms 20% behind. With only one attack per round this isn't looking so good - but that's first level. At second they gain Action Surge, closing about half the gap assuming the textbook 6 encounters, 2 short rests/day. At third they gain a subclass which (depending on subclass) finishes closing the gap. At fourth it's an ASI or a feat - and at 5th level they get their second attack, doubling their DPR and permanently ending the one reason the AD&D fighter was doing more damage.
Of course all of this is largely irrelevant when an AD&D ogre had 19 hp, a 3.5 ogre had 29hp, and a 5e ogre has 59hp. Fighter damage might not have been drastically reduced but hps were massively upped so the effect is the same. The fighter might as well be waving a nerf bat.
Well, that was my point, which you got to at the end. Sure, the 2e fighter might have been equal to the 5e fighter, but, since your opponent had 1/3 the HP, it does mean that the 2e fighter comes out WAY ahead. And, you're also forgetting that against that Ogre, I'm not doing 1d8+3, I'm doing 1d12+3. Additionally, the notion of a 17 Str fighter is pretty laughable to be honest. That 2e fighter will almost always have an 18/percentile strength, which massively ups the damage output, and will most likely be using a second weapon (because, well, if you're playing 2e, why would you not use 2 weapon fighting?) which, again, jacks up our fighter's raw damage output against opponents that are significantly easier to kill.
2e really was the fighter edition. And, let's not forget the other side of the equation as well. Those casters, of which your group probably only had 2, had very, very limited resources. I'm struggling to think of a mass damage spell in the 2e PHB before fireball. I'm sure there must have been some, but, none jump out at me from memory. Burning hands I suppose - which was only really good against maybe 2 opponents. The cleric, OTOH, had basically no damage dealing spells at all. Spiritual hammer at 2nd? Was there any damage dealing spells for clerics before 2nd level? In 5e, our 1st level wizard and quite possibly our 1st level cleric both have area of effect damage spells right out of the chute. Thunderwave is a good example. I'm sure there are others.
Like I said, track it in your next couple of sessions. Just see how much total damage the casters are doing vs the non-casters. It's shocking.
