I hear all the time the 2024 revision pushed the power level of classes over the edge compared to 2014. The better abilities, Origin Feats, and Weapon Masteries did increase character power in some builds, but there are also quite a few nerfs that limit character strength in 2024. The nerf to GWM really hurts reckless Barbarians, the Paladin smite nerf is hated for stopping the Paladin's ability to just wreck solo monsters, the nerf to Druid hit points in Wild Shape made them quite a bit more fragile, and the SS nerf really cut the damage on characters that stay way from melee. The nerf of Counterspell is also a strong check on caster balance, and the fact that you can shut Absorb Elements out of your game by only using the 2024 PH spells is another limit on caster strength. There is still only a small chance of a TPK or character death, but that was always the case in D&D 5E. I would not characterize characters as failure-proof at this time. Character frailty and damage is still mostly determined by the build of the character. If you have people that focus on that when they build their characters, it will be harder to challenge them with appropriate level encounters. Still, it's not impossible. I give my monsters Toughness (2 extra HP per die) when I DM for groups where the characters hit above their level. It is surprising how much difference that makes.