A fighter isn't limited to 2 swings of a sword per day. A miss with a martial attack doesn't mean that your character is "spent" for the day.
No, but on average two hits from an enemy is enough to "spend" a first level fighter in an old school game. Either for the fight or just forever. The front line martials are more at the mercy of enemy rolls. The back line casters are more at the mercy of how successful their spells are.
But in practice the game should be more about making good decisions and testing your luck judiciously. If you just constantly push into combat you will almost certainly die. But that's true even of WotC editions (as you've apparently discovered, per your comment about all but one of your 5E games also ending in TPKs). Even if the rules and death conditions are more forgiving, if you continually push your luck eventually it runs out. It's just a question of how soon rather than whether.
Let me put it this way. I had a 3rd level SD wizard with one attack spell (pregenerated at a convention). I missed with my one attack spell on the 1st round of the first combat. The rest of the session, the only thing I could contribute in a fight was a dagger attack, which paired nicely with my single digit HP and AC 11.
Sure, that could've been a poorly designed character with a bad spell loadout. But heck, let me at least get one spell to work if I'm the darned wizard.
Assuming that game ran by the normal rules, you had five spells and a better than 50/50 chance to cast each one. Plus probably at least one Luck token for a re-roll.
Compare to any TSR edition, where you'd have three spells, and any offensive spells other than Sleep or Magic Missile would have a 25%-35% chance of failure (assuming the usual monsters you'd expect to see at low level) through the target making its save. And you would have zero ability to roll well and cast the spell again. Zero ability to roll a crit casting and get extra effects.
A 3rd ed Wizard would have three leveled spells plus four castings of their cantrips. But they have the same D4 HD as a Shadowdark Wizard, in a game where enemies do more damage.
A 5E Wizard would have six leveled spells plus unlimited castings of their cantrips. They get upgraded to a D6 HD, but again enemy damage has increased, so there's not much durability gain if any from higher HP. It's really just the more generous death rules that help them. And Shadowdark has more generous death rules than the TSR editions.
Just going by the math, the WotC editions give the Wizard a few more spells than Shadowdark (especially 5E giving unlimited cantrips), but Shadowdark casters have a couple of advantages WotC casters don't, and more magic than they do at the same level in any TSR version. So just looking at the black and white rules, it appears that Shadowdark casters are less powerful and durable than 5E casters, but comparable at low levels to 3E casters, and more powerful than equivalent-leveled TSR era casters.