That is how one plays 2E. Who ever played AD&D by the book?
Sure. But the other thing is that all the reflexive responses are just convincing me that the people responding never played nearly as much 1e/2e as I did. I've got probably 2000+ hours of playing 1e/2e as a thief, and the class is only really balanced between about 1200 and 2000 xp when you are second level and get 2HD and other classes are still just 1st level. At practically every other point, you are weaker than every other class. It's this recognition that the thief was useless that lead to all the radical improvements that gave us the 3e Rogue.
It's practically criminal and abusive to allow a naive young RPer to play a thief in 2e, which the OP seems to recognize when he suggests that a DM that would use the RAW is "monstrous".
But consider the suggestion that of course the fighter is better at combat than the thief because that's it's shtick whereas the thief is skilled at the exploration pillar. Hogwash. The thief is arguably worse than the fighter at trap detection, and is clearly the fourth strongest class in exploration play among the traditional four. But worse, it's not just that the fighter is a little better in combat than the thief, it's that the thief is useless in combat after about 5th level. The thief is also by a long distance the worst character for combat. And combat will always be a thing so being useless in combat is pretty harsh.
The trouble with the thief in exploration play is no good thief player uses their thief skills except as saving throws. At low levels, your thief skills are so unreliable that proposing to climb walls or find and remove traps is in the medium term just the first stage of rolling up a new character. You can't trust them at low levels because they will usually fail. Instead, you use them as saving throws when proposing strategies that don't depend on the dice - like probing ahead with a 10' pole fails. But the trouble of course is that any character can propose those strategies regardless of class. And as the good people who wrote 'The Gamers' noted in the joke, sometimes the best strategy with a trap was let the fighter find and disarm it because unlike the thief the fighter wasn't squishy. You weren't good at exploration play as a thief because you saving throws were worse than every other class. You weren't good at exploration play as a thief because you fewer NWP's than every other class.
Most importantly you weren't good at exploration play as a thief because about the time that your thief abilities start to become reliable, they can all be replaced easily by trivial expenditure of spells. Your climb walls as a 20th level thief, is strictly inferior to the 1st level M-U spell 'Spider Climb'. You 'Hide in Shadows' as a 20th level thief, is inferior to the 2nd level M-U spell 'Invisibility'. Your much less helpful at finding traps, than a Cleric that casts the 2nd level spell 'Find Traps' or a M-U that has a wand of secret door and trap detection. Moving silently is largely useless in a party that can't, and if the party really needed to move silently well there is a spell for that too. And arguably finding a trap just is replaced by a Cure Wounds spell anyway. So what you can try to do as a high level thief is save the spell slots of your useful party members for other things, but what you eventually discover is that the number of spell slots you are saving is less than the number of spell slots you would have if you were an equivalent level caster - and you'd be useful for other things as well.
And there isn't really a counter argument to this about the player's skillful play, because sure you can use flasks of flaming oil and apply poison to your weapons and I have done that in attempts to stay relevant playing the thief, but you aren't really that much more skillful at those sorts of things than other party members. It's just you have to rely on those sorts of tricks to be useful. It's a class that offers almost no character abilities and it's all about player ability.
But as for your specific argument, it is an obvious fallacy to say that there is not a problem because you can always change or ignore the RAW. After a while, if you've really played lots of 1e/2e AD&D you either have house ruled it to the point it's increasingly not recognizable in attempts to fix the problems or you are going to be really frustrated.
I have a lot of nostalgia for 1e/2e AD&D. There are aspects of it I still love and wish I could find a way to import into modern editions - like the exponential increases in XP per level, some of the play patterns encouraged by gold for XP (but not all of them), the 1e weapon vs. AC modifiers, etc. It's great to have fun with the game. But it's funny to listen to people declaring a DM would be "monstrous" for playing with the RAW, while praising how great the system is.
