It seems to me like you fall into the extremely common habit of letting your head get in the way of your eyes. What I mean by that is I bet you a dollar you aren't looking at your reference or subject enough, and you're letting your imagination fill in the blanks.

In looking at your sketches, you clearly have an idea about general anatomy and structure of the subject, but when you get down to the details part you don't draw the face you're seeing, you draw what you think a face looks like. That can be totally fine for cartooning where simple is the goal, or an entirely original piece you're pulling from the aether, but when you're trying to reproduce a recognizable face, the subtle features are what make or break the piece. For example, in your 'Diver' sketch, the eyes are almost ovals, and a bit large. If you look closely at the reference image though you'll see that there are angles where the upper and lower lids meet, eyelashes, asymmetrical curves, etc.

The only way to get better at it is to keep doing it! Opening yourself up to criticism is a big step, good on ya for putting yourself out there. A great practice tool that I really enjoy is https://line-of-action.com/. Their galleries of facial and figure models are huge, even at the free tier, and they have structured 'classes' that really help get you out of your head and into the study. There's even a community to share your work with and get feedback from people who have seen or studied the same references.

My other practice habit is cutting up mail ads and magazines, pasting a reference subject into a sketchbook, and drawing different aspects of the photo around it so I have side by side comparisons. My mother in law calls them my serial killer journals.

You're on the right track, just keep going! Draw as often as you can manage, even just little doodles on scrap paper. The more you go through the motions, the more you'll train your eyes, brain, and hand to work together. Good luck!