Break down your shot. There are a lot of things going on in an archery shot sequence.
The best advice I received as a trad nube was to first work on left/right variability. Shoot at a backstop (I used a compressed bale of hay) that has a vertical line down the middle of it. I wrapped my bale in plastic wrap (heavy duty Saran Wrap to "weatherize" it). Then I placed a long piece of masking tape vertically down the middle of it (standing the bale on the short edge, so it stands "tall"). I then place another piece of masking tape across the "short" axis of the bale about 4-5" from the bottom, the top and one across the middle (all horizontally across the bale's short axis).
My "standard" distance is 20 yards, but I practice at 10, 15, 20, 25 and 30, and then move back to find my "point" on distance.
I shoot 3 under.
I put the arrow point on the lowest tape intersection and then focus on my release. I really don't care if the arrow/impact has high / low variation, but I AM interested in L/R variation. This isn't really "blank bale" shooting, as I am not shooting at a blank target. I am putting the arrow tip on a "mark" (tape intersection). After that shot sequence step of "aiming", I focus on DEVELOPING BACK TENSION (not neck/trapezoid stress), RELEASE, and BOW ARM FOLLOW THROUGH. I take 5 shots.
When I first started trad shooting, (3+ years ago), I didn't have groups. I had "clusters" that were mostly on the target. As time/practice passed, I'd notice 3/5 arrows in a "group", then time passed, and I got 4/5 arrows in a group, then sometimes 5/5. Then the groups got smaller.
Once I got a representative 5 shot group, I was able to experiment with arrow tuning by trying different shafts (I own Easton xx75 aluminum Tributes in 1816, 1916, and 2016. All with 4" parabolic x 3 /shaft feathers.). I also experimented with shaft tip weights. This doesn't really help "precision", but it does help in adjusting L/R (weak/strong) issues. I also experimented with strike plate thickness. But, GROUP SIZE, was addressed and improved by this semi-blank bale arrow point-on-a-mark drill. I was told that if you get your release a follow through addressed (isolated by this drill), accuracy will improve. I was told L/R practice would be the biggest improvement to work on, and that horizontal (up/down) issues will follow. "They" were right.
You don't HAVE to use the horizontal tape lines and use a point-on aiming point. Perhaps this is even too much to process. Break it down further, and just put the arrow tip on the vertical line- anywhere, and focus on release. This still isn't true "blank bale" shooting, as you are focusing (and aiming) at a vertical line. True blank bale shooting breaks the shot sequence down to the most elemental issue of just plunking arrows into a safe backstop, while you solely focus on release. If you get feet positioned right, you can do this with your eyes closed, really "feel" the release. So, breaking down a shot sequence to the most basic element IS very helpful (and recommended). The drill of aiming at a mark or tape intersection is has an aiming component-so it MAY be too much at first. Don't be afraid to "simplify" the drill down to "just vertical" or "true blank bale/not aiming" release drills. I would wager any of these drills will help your group size and consistency.
I also do another drill, but without my bow. It's really "blank bale shooting" without a bow. I use it to focus on back tension, and release/follow through of my drawing arm. I shoot right handed (draw with right hand). I grab my left and right hand finger tips across my upper chest/collar bone area and then raise my right hand up to my anchor point (my left hand is "the string"), and pull horizontally equally laterally outward (simulating drawing, or holding, the string). I focus on having an upright, stress-free neck, feeling my back muscles pull. Then I gradually "release" with my right hand. I want to see/feel a quick and natural recoiling of my right hand. I don't try to touch my right shoulder or face with my draw hand as an "end point". I just let it "pop" out from the release about 6"(?) like a spring, or a "cut rope that was under tension." In "The Wedge" video series on youtube, they call this a "natural release." I don't do it every time, but that is what I'm trying to achieve.
with this bowless drill, I am trying to "breakdown" one/two aspects of my shot sequence: my back tension and my "cut-rope draw hand release pop-back." I can do this drill just about anywhere ( at work). It also develops muscle tone in your back, shoulders and fingers. I find it very useful for my needs. It's helpful to do this in front of a mirror too, to verify an erect (stress free) head position, and "pop back" of the draw hand upon "release".
Accuracy improvement in any shooting sport is a journey. It requires patience, a plan, recording notes (things you tried, and results), and future thoughts on shot/form analysis. You'll improve with practice time and desire.
So, be patient. Breakdown your shot sequence. Don't try to make a "perfect shot." Work on making "perfect form"-and the perfect shot will follow.
Another benefit from the drill of shooting at a vertical-horizontal line/intersection is that if you do it at various distances, you also learn about the gap (or trajectory) your arrow has above that aiming point, whether you shoot at 10, 15, 20, 25, or 30 yards. Write down your gaps (arrow impact height about aiming point) with any arrow/tip weight at 10, 15, 20, 15, 30+ yards. You will develop useful trajectory curves which will aid in "up/down" variables later. It will also help you decide on the best compromise for selection of arrow shaft and tip weight. A big reference point on these trajectory / gap curves is noting your nock position above perpendicular (higher nock, lower gap) for each distance/arrow shaft/tip weight etc.
There are excellent youtube videos available. I like many, but Col. Jimmy Blackmon and Vabowdog (Dewayne Martin) have EXCELLENT videos on gapping and nock position for tuning ( I believe both were national trad archery champions in 3d or vegas targets, so they know what they are doing). Arnie Moe has several excellent videos on youtube on archery form (he is a regular visitor/poster on this website-a great "local" resource.")
Shooting at a vertical line (or "point-on" at the tape intersection), takes half the variables out. You don't get distracted with up/down AND L/R issues. To me, that's how you improve. I was able to find things that were hurting my accuracy, as I had twice the focus on half the variables. It works for me-and I still do it.
GO VERTICAL! Good luck. Be patient.