Interacting with NPCs and the environment, items, levers, floor tiles, drawers etc through direct conversation with NPCs and through saying what your character does “I lift the rug, is there anything under there?” is not hand-waving.
It’s, uh, let’s call it “diegetic mechanics”, and things like dice rolls, attack checks, HP, fate counters, numbers on a sheet etc, those are “symbolic mechanics”.
My own preference is to do everything diegetically if it can be done diegetically, which means… probably fighting and disease and stuff like that, climbing, all kinds of actually physically dangerous stuff, that I wanna leave to remain on the symbolic layer only.
Now, using diegetic mechanics (a.k.a. “saying what you do”) for things like finding a secret door is pretty darn hard if your prep only says “secret door here, 1/6 to find” or if you don’t even have any prep at all, just wingin’ it. If you instead have something like “the bookcase can swing away leading to a passage behind it”, that’s something you can work with. So searching for traps & treasures is something that is helped by prep.
For NPC convos, you’ve got to ask yourself two questions. Mentally, in your own mind, silently, but do not skip this step.
For example, the PC knights have agreed to an NPC village smith’s request that they (PCs) fight a lizard in the marsh. The PCs ask for directions to the marsh. The smith knows those directions. Just give ‘em! Do not drag it out.
But if there actually is a reason, for example the NPC doesn’t really know but doesn’t immediately wanna let on that they are clueless, or the NPC knows but doesn’t want it well-known that they have dealings in the marsh, or…
There’s a reason why the Stella Adler school of acting has you asking “what’s my motivation”—having this sort of clarity about a situation makes these sort of conversations immediately sharp and interesting, and letting the PCs gradually discover the motivation or fail to discover it or manage to convince them or bribe or find out the truth or give up or succeed or come back later or ask for something else or get deceived or manage to deceive or threaten or…
It can play out in so many amazingly rich and nuanced different directions, I’d never wanna boil that down to just a number and a check! It’s not about thespian ability or about writer’s ability or about confidence (although playing RPGs in this style might help you with all three). Don’t punish nerves or hesitation or bad poker face; what you instead need to listen for is the actual arguments, “tactics”, leverage, and reasons.
And also when the conversation start to repeat, that’s a failure, of that line of conversation at least.
Good luck!