I'm sure you've heard this D&D is 40 years old. While I haven't been playing it for all 40 of those years I have been playing for most of them. I was a self-taught DM, it was a year and a half before I gamed with someone I wasn't introducing the game to, so some weirdness creeped into my early games due to isolation and inexperience.
We played on big sheets of graph paper where 1 inch = 10'. We'd march the figures around a growing game board. we were savvy enough to realize each figure didn't actually take up 10' and generally only worried about where the lead figure was unless folks split up.
There was a while where my rulebooks were the original basic set, Greyhawk, Blackmoor, Eldritch Wizardry, and the Dungeon Master Guide. Play went over 3rd level in that period but not too far , O think the most powerful character we had was an elf fighter/Magic-users of 4/3. I didn't bay an eye at tough monsters vs the characters, sure 1st level was mostly 1st level monsters but if I felt a Minotaur or Dragon would enjoy a spot on the 1st or 2nd level of a dungeon that's where it was (I'm still prone to a bit of that).
Gargolyles were treated like another race of folk just like goblins and orcs, something had to challenge higher level characters right? I know I had "younger" ones with fewer hitdice that could be harmed with normal weapons so they weren't TPK material but for a while those pesky gargoyles were the monsters to beat and the few that had them as minions were truely spooky stuff.
If players could surprise attack monsters I usually let them win through clever descriptive action, heroes did it in mythology all the time, why not player characters? A little of that lingered for years and I still let a player pull a fast one now and again but they have to be really lucky and creative.
Phantasmal Forces was a king of spells. Sure a creation went "whiff" if hit in combat but if the foe missed the fight went on and being killed by an illusionary phantom still brought death. The party managed to off a red dragon with a phantasmal monster once due to the dragon missing the phantasm over and over again.
There were other oddities I can't recall at the moment and others I discovered as a I met more players, back then each group of D&D players was a sort of cargo cult with a limited range of books and not much experience and those were the days indeed.