Yay, with the caveat that they need to be properly foreshadowed so players have a chance to respond to them. Notice how, in Indiana Jones, Indy usually sees the skeleton of some poor sap who got screwed over by the trap, or else the traps are clearly telegraphed by decorated tiles, or a pedestal that screams “something’s gonna happen if you pick up this idol.” That doesn’t mean the party has to be directly told when their are traps in the room, but they should be able to figure it out just by environmental context cues. It should feel like a Dark Souls game, where when you walk into a trap, your reaction is “I totally should have seen that coming!” and not “wow, this game is really unfair.” Part of how those games do it is by using consistent tells, so after the first time you walk into one, you know what to look for to avoid walking into another. Maybe in this dungeon, spear traps always come out of statues. But not every statue is a spear trap. And there's a boatload of statues in this dungeon. Now, as long as players see that first skeleton impaled by a sprung spear trap near a statue at the beginning of the dungeon, the’re going to be real cautious around statues. Or if they’re not, they definitely will be after the first time one of them gets nailed by the exact same trap that got the skeleton. They can learn from the environment, ok, statues in this dungeon mean there might be a spear trap. Now they have the tools to avoid them. Now it’s not just a gotcha or an hp tax, it’s a dungeon-wide incentive for players to pay attention to the environment.
Also, traps need to give the players a split second to react. It should never just be “You stepped on a pressure plate, make a Dexterity save or take 5 damage.” It should be, “You feel the tile of the floor sink slightly beneath your weight and hear the click as some unknown mechanism settles into place. What do you do?” Then, based on what they do, maybe give advantage or disadvantage on the save.
I don't entirely agree with any of this.
I'm not designing the dungeon as a "game" and traps are one of the areas where that really shows up. Traps are placed by intelligent creatures in intelligent locations. They are created for a certain purpose, and usually that purpose is related to something other than PC adventurers.
For example, traps to prevent thieves in the city are tailored to protect against the typical thieves of the city. Probably 1st to 3rd level thieves. Wealthier individuals would have more elaborate traps to protect more valuable things, and they would be harder to detect and/or disarm, and more disabling.
On the other hand, the tomb of an ancient wizard that wants to keep his stuff for eternity. Traps galore, magical and mundane, and very hard to detect and/or disable, and most of them designed to kill. The "foreshadowing" is the fact that the characters are choosing to enter a tomb built for/by an wizard of some power. Oh, and the fact that it has remained unsuccessfully plundered for thousands of years by other foolish adventurers just like them.
Now there may be some similarities in the traps, because the same trap-maker made them. But any decent trap-maker will also use that as a gotcha, with one being different for no reason (and any high level tomb robber will be expecting that).
The "split second to react" is called a saving throw. Depending on what they are doing, it could be more than that. But there's no "should be" about it. Again, it's all dependent upon who the trap was built by, for what purpose, and the skill of the creatures they expected to trigger the trap.
In many cases, the only reason the PCs survive (actually, they are involved in one such dungeon right now), is because the traps have either been sprung, or the tomb is so old they aren't functioning properly anymore. In this case it's both - many tomb robbers have attempted (and failed), but in the process set off more and more of the traps. Those traps that they could get around, or that reset continued to cause difficulty for later ones. But a portion of the tomb has been compromised by the elements. What was once sealed and dry now has a stream running through it, and hundreds of years of humidity have caused the wooden portions of the tomb to rot away, and iron and steel portions to rust, and poisons have lost their potency. The traps are often still dangerous, but not anywhere close to the degree they once were.
The second part of the tomb was more protected from the elements although it too had been plundered. The foreshadowing was the dead corpses they found, some of them still impaled a la "Indiana Jones"
Because the world is full of tomb robbers (adventurers, monsters, etc.), magic, and the elements, a great many tombs are in this state to one degree or another. But none of this has anything to do with designing for the PCs. It's all based on a world-building approach and what makes sense. And the players have to consider that when they decide they're going to enter someplace or not. Right now they are leaving the tomb because they've decided it looks too dangerous to continue. They will return later, possibly in a year or more (in-world and game time) like they've done before.
