It's funny how we can convince ourselves of anything, especially with all the info and influencers out there doing "studies". My brain is over ran by the paralysis by analysis bug on all sorts of topics
I've chased a LOT of rabbit holes. IMO/IME you MUST get the mechanics right before you chase anything else.
On a new rifle/barrel, a couple of wet patches with your favorite solvent just to make sure there's no machining shavings/small chips in the bore. I like to follow that with 2-3 patches soaked in rubbing alcohol, and 3-4 dry patches then call it done. A used rifle gets a few passes with a solvent on a jag, then some bronze-brush scrubbing, a few more patches to clear that out, then a tight patch filled w/Iosso or JB bore paste and 20-50 passes, re-applying to the patch every 10-15 passes. I'm not so concerned with getting down to "bare metal" once I know what I've got, but, I need to see bare-metal at least once for a reference. I've got 2 barrels in particular that are UGLY to look at but shoot quite well. A ~$90 Teslong bore scope can tell you a lot about what going on in your bore, just don't forget to look at what targets are telling you as well.
The screws holding on the scope bases and holding the action in place get a little polishing to remove any bluing on the very end, they should be shiny. Then coat them with a sharpie, install, torque to spec, then remove and see if there are any marks in the sharpie that might indicate the end of the screw/bolt is touching where it shouldn't be. There should be 0 pressure on the very end of the screw/bolt, the threads and head of the fastener should bear 100% of the "clamp".
Trigger retention pins, safety lever, bolt release, fixed blade ejector should all be checked. Retention pins should be centered, you can add a little nail polish to keep them in place, it can be colored if you want to know in the future whether it's been done or not. The bolt release, safety, and fixed blade ejector should all move freely, if they're binding, figure out where they're rubbing and lightly file away the problem. Same for the bolt in the bolt-handle journal of the stock, it should never rub there, but, sometimes it does and needs a remedy. A bit of grease on the mating surface of the bolt lugs, cycle the bolt and look @ the swipes in the grease to see if you've got good contact or a problem. You could also sharpie the mating surface if you're having a hard time getting the bolt in/out without disturbing the grease swipes.
The barreled action should sit flush in it's inlet without any "rocking" or "teetering". If it's not flat but is teetering, find the problem and solve it by removing the pivot point (lightly file/dremel) or adding bedding to raise everything above the pivot. I like a barrel to be either fully floating (bedded to the end of the shank and then a generous float), or fully supported IF it's inconsistent when floated.
The internal mag box and/or bottom metal should not flex or bind. Run the bolt back and forth with the bottom metal out and the bottom metal installed. If it feels like there's a "hitch" or hesitation in the bolt cycle, something is binding and/or flexing the action.
On a new rifle or re-barrel where everything has been disassembled I take about 90min or so to tear-down and get everything put back together ensuring nothing is touching or torquing where it shouldn't be. Some will bed the scope bases to the receiver and skim-bed the scope in the rings, I don't go that far. I do put a good dose of gel-type nail polish on the action and the scope bases then torque in place. Kind of like bedding I suppose but much quicker and less mess. I lay a lapping bar into the scope rings and if it moves freely, I put the scope on, if not, I'll lap a bit until the finish inside the rings shows me full or nearly full contact.
Rifle/scope combinations properly assembled and stress-free will often shoot multiple loads quite well and mostly to the same POA/POI.
None of the above is a guarantee a rifle will shoot well, but, it does shorten up the list of things a person needs to look for if it doesn't. If the above is all correct you're down to issues with the bore (pits/corrosion/excessive fouling), crown, stability of the projectile @ current twist and velocity, or the scope itself having issues.