I started a few years later, around the mid-1980s with AD&D in high school. My take-away from old-school D&D was smart & cautious play was the assumed default, i.e. if you did dumb things at critical moments your PC would die. Before making it to 2nd level.
Because before D&D is anything else, it's a game. And you're not supposed to play a PC to lose -- no matter what their stats are.
Sure, your INT 5 PC might talk like "ME AM THUD! UMM... HUZZAH!". But that didn't mean you played him stupid when it counted. You played to win, i.e get gold/XP and level up. You played smart -- to the best of your ability -- while sounding like a complete idiot.
Or at least that was the ideal. Sometimes you were bored -- or, you know, a teenager -- and smart & cautious went right out the window, regardless of how high PCs INT and WIS were. You went in fireballs-a-blazin'. Before estimating the volume of the room and/or corridor...
Actually, things haven't changed all that much for my group.