Just to get it out of the way, I don't watch CR, so I don't know if this is a specific reference, and am just speaking about D&D in general. :)
Kind of inevitable with most D&D games. If you design adventures around having a series of more-or-less balanced encounters, almost always combat, where player characters are expected to be stressed but not generally killed the vast majority of the time... both the players and their characters are going to have the expectation that they can just do that.
So you need to manage those expectations. Make it clear up front, and either run the game so that death is a real threat more of the time, or find other ways to make it crystal clear when it is.
(Or just don't make things lethal and find other consequences for failure. Or whatever you'd like, my point is just to get folks on the same page.)
IMO, this is an issue specific to 4e and 5e. In 3.5 and older, it wasn't as expected that D&D would always be balanced with winnable fights. Often you'd have horror moments in modules/campaigns where you were expected to run away or die.
At least the way my dad taught the game to me, 2e was almost survival horror for lower level characters.
Gary Gygax dungeons were infamous for the "there's 3 doors. Behind door 1 is a swarm of giant poisonous killer bees, behind door 2 is an insta kill trap and behind door 3 is a tunnel leading to a chest full of gold and gems" situation without any way to distinguish the doors.
It's definitely something that's a part of newer D&D, though it's debatable when it started. It was inarguably a part of 4th edition, I think it was here by 3rd edition, and there's even a case to be made that 2e was headed in that direction with some of the supplements.
Anyway, your dad was right. :P During 2e, that was still a big part of the game. It's part of the differentiation between "old school" and "new school" D&D. Whatever I think of any particular edition, I think both approaches are rad for different reasons. :)
It's just the mismatch of expectations that would be a problem. It sucks to die because you were expecting another epic set piece battle, and it also sucks to try to come up with a clever solution to avoid an encounter just to end up not doing much or getting railroaded.
@Lianodel@ttrpg.network its a meme,dude. We as a party were in a high Level Dungeon as mid level chars… and dm told us repeatedly if we really sure about this…
So, Matt has had a couple of moments where it is, before combat, looking like the players are FAR outmatched. Aaand someone’s fave purple character paid for not doing the mental maths. I feel that is how he makes it clear that you PROBABLY don’t want to take the baddies on.
My fav Matt surprised moment isn’t the party going into a fight they shouldn’t have, but how Travis decided to get them out of a tough fight in Nicodranas in Campaign 2. Totally sent campaign in a new but fun direction. Bonus that the next episode was live on stage and the cast got to play dress-up.