What Rusty said.
I'm not overly picky on triggers. I have some light/clean ones. I have some heavy/creepy/gritty ones. IMHO, if you can learn to shoot well with a cruddy trigger, you've learned actual trigger control.
This book was a complete mind shift for me on triggers:
Once I read and practiced what he talks about in that book with trigger control, I found that I cared a whole lot less how mechanically light a trigger was, and whole lot more about how "clean" it would break, and how reliable/consistent it was. If it breaks at 5lbs exactly, every time, I can shoot that a whole lot better than a trigger that varies from 1.5 lbs to 3lbs from shot to shot.
I sure haven't worked with tons of rifles, but when I get one that's hard headed, I usually go to my loading bench first and try the tricks of the trade there. If I can't get the response there that I'm looking for, I check for crown damage, bore problems, and bedding problems, in that order. Scope mounts/tightness/integrity get checked early on, too. I'll often change out to a known good optic to rule out the scope itself, too.
On factory rifles that I see anymore, my biggest suspect is usually structural integrity of what is often a cheap plastic stock, to include contact points on the barrel and bedding (both quality of work and HOW it's bedded).
I've had some real stubborn rifles come around through carefully working through all this. I "rescued" a rifle of my dad's when it started giving him issues. I pillared/bedded it, floated it, and worked a new load for it. Went from 5" at 100 to 4" at 300.
It can be done....but it's work.