despite this still being a big struggle for me on some days, i'd like to think i do!! also, getting the majority of the likeness is already such a feat and i hope you realize that :) a big part of getting better at drawing truly is of course just repetition and practice so if you're already getting so much right on your own, i'm sure your eye for it will improve either way! but, to help you along, here are some extra tips ❤️

(btw i'm gonna assume this is for drawing realism/portrait-related art, because my answer would be very different if it's not.. but if you'd like to hear tips on that too, just say the word and i'll do my best for you!!)

first, my biggest help with this has always been mirroring the canvas. when you're focused on drawing from reference, your brain will at some point get stuck in what you've drawn so far and it will become harder to see your work from an "objective" perspective. mirroring the canvas (and the ref) can help a lot in spotting problem areas because your brain isn't used to this perspective, causing inconsistencies to stand out more.

alternatively, you can also flip the canvas upside down! if you truly want something to look like the reference, sometimes it's better to see the subject as simply a bunch of shapes and anchor points, instead of a recognizable face. us humans are trained on recognizing and being very focused on facial features by evolution, which is useful in a lot of situations but can actually be very detrimental when drawing accurately from reference. even if you want to draw an eye exactly the way it looks in the reference, your brain will at the same time be trying to just draw an eye the way it thinks an eye is "supposed" to look instead, because it is very confident in the way eyes are "supposed" to look due to all that training! this is why in realism it can be more useful to focus on the shapes of shadows and colors, and the relative dimensions of those shapes, than on "i am now drawing an eye. i am now drawing a nose". and if you struggle doing that, flipping the canvas upside down makes it easier to make it look more abstract to your brain!

also for the same reason, i recommend that when you start with a sketch, you keep your canvas pretty small/zoomed out, and only focus on the big shapes first. zooming in too soon will make you lose sight of relative proportions and composition; only start zooming in when you're certain the sketch is accurate enough.

now, you also say you're staunchly opposed to tracing. while i definitely try to stay away from tracing for most of my art, i would actually like to also make a case for it!! my biggest gripe with tracing is that it can make your eyes/brain lazy if you depend on it, which is definitely unhelpful but not... problematic, necessarily? unless you're lying about it for profit, or talking about tracing someone else's art; there's obviously much bigger problems with that. but i do feel like tracing, or at least certain techniques adjacent to it, can be super helpful if you're struggling!

the first technique is tracing in rough lines over your ref in a new layer to "practice" the shapes you see. this is not about tracing every little bump and eyelash, but about trying to discern the structure of what you are going to draw. take note of the space between the bottom lip and the chin, the shape of the shadows along the cheekbone, the height and angle of the eyeline, the planes of the face that catch the light, etc... you're essentially training yourself to recognize and break up the face into the shapes that you will need to draw yourself eventually as well. this can also be helpful in getting a feel for certain angles or curves; don't underestimate the importance of muscle memory! when you're done tracing/practicing, you can then open a new canvas and start over fresh :) you can keep the line layer on in your ref image if you want a lil extra guidance in seeing and copying those shapes clearly, or you can hide it and just try it yourself this time of course!

another technique is to not trace exactly, but to mark some of the important edges of features on your ref with small dots, and then use that dot layer as the base for your own sketch. think corners of mouth, outside edges of nostrils, corners of eyes, tip of chin and forehead. this way you will still have to do plenty of work on your own, but you do have a general guide to work from!!

finally, if you really don't want to do any kind of tracing on your ref image but still struggle to see why your own drawing looks so different, i recommend two things i almost always do:
-make sure your ref image and canvas are the exact same size so you can position them next to each other and compare them more accurately (to ensure this, i personally always position the picture i want to draw on a canvas of the same size that my final art will be, move and zoom it until i'm happy with the composition, and then use the png of that canvas as my ref)
-use a grid!! i personally use procreate and there's a built-in function for it under "drawing guide" (and since i always have my ref image in another procreate canvas as well, i can easily apply the same grid there too!). i'm not sure about other programs but it's fairly easy to make one yourself and paste it on top of your ref image too. essentially, what a grid does is break up the ref and give your eyes more anchor points to spot mistakes. think of it this way: when you have two very big pieces of paper and one has a little dot on it, it's much harder to then place that dot on the exact same spot on the other piece of paper. but when both pieces of paper are very small, it's much easier for your eyes to go "ah, this dot is supposed to be just a little to the right of the vertical center line, and about two thirds of the way down", and estimate those distances correctly. now, using a grid can definitely also bring along the same problems as tracing bc it allows your eyes and brain to be a little lazier!! so try to keep the grid pretty big in order to still get some training out of it yourself. i personally like to use a nice big grid to help me get my initial sketch right, and then i'll turn it off once i'm pleased so that i can just focus on painting and depending on my own skills. but if i ever feel like something is off, i can turn it back on, or even make it a bit smaller to check for details :)

i'd like to emphasize that the techniques i described are honestly something a lot of traditional realism artists do for portraits as well; since there is so much rendering to do anyway, it's nice to know that at least your proportions are correct (especially since they cant easily digitally move features around later on). doing things like this does not negate all of the work you put in at all, imo! but of course you are completely free to make your own choices in what you do and do not feel comfortable with :)

in the end, overall id say practice and time still are most useful because those are truly the only things that will get your skills to consistently and reliably improve, but that's a boring answer that you probably already knew yourself, so i hope these tips help for now <3

oh and as a bonus here's a vid on youtube that talks more about how to get proportions right :https://www.youtube.com/watch?v=1J7RQvKnWf4
i love watching other artists/art channels explain stuff because i'm very much a visual learner myself so i can imagine that watching some videos can be more useful than simply reading my answer!!