Having played a lot of 5E, I would say that your impression and squeen's impression that 5E play is inconsequential (in the sense that it avoids having serious consequences) is spot-on. It's not that a DM *can't* present players with something like a machine that, if you place two limbs in its two holes, permanently switches them; and if you place only one limb in it, severs it. You can do that--but it feels un-idiomatic for 5E, because generally in 5E everything resets with a good night's sleep. (There are exceptions but they are haphazard.)I have a hard time putting my finger on it, but it feels like it is without weight. Replenishing resources is trivial, traversal is de-emphasized (and many characters have access to teleportation and similar abilities from level 1), equipment is a matter of optimization to the character's skillset rather than a tradeoff between weight and utility. Combat is at least at low levels as dangerous as any OSR game blow for blow but getting back up if knocked out is also trivial. The abundance and general weakness of spells (many are just missile attacks for mages) makes magic seem more like pyrotechnics than deadly sorcery.
It can be *modified* to challenge or frustrate--imagine someone running a 5E variant where scaling a 30' wall takes climbing hooks, special shoes, and 10 minutes, instead of 6 seconds and a d20 roll. But why reinvent the wheel instead of playing a game with challenge and frustration built in?