Mundane content is the biggest culprit whether you follow and apply elements of composition or not.
the problem with these is they don't really have much of a subject. they are just snap shots.
I think you just need to focus on finding a more interesting subject.
A trash can? And you didn't even police up the trash around it.
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It seems to me you've been handed a mixed bag here - some wonderful advice on things of a technical nature and some not so great advice on things of an artistic nature.
As a new subscriber here, I've been reading quite a lot and commenting little, but I'm noticing what seems to be a pattern here from my perspective. There are some people here (the majority who respond) who can offer wonderful technical advice, knowledge, and experience. I wouldn't hesitate to ask a question of that nature on this forum. As for the creative, artistic side of things? I'm less convinced and have actually seen far more here that leads me to believe this isn't the place to be soliciting advice of that kind.
Clearly your photos are not snapshots. There's a great deal to be said for shooting what's around you and the commentary that can be made in this chronicling of the seemingly mundane and banal. (William Eggleston, anyone?) The garbage littered trash can with the "Keep Omaha Beautiful" sign was clever enough. That doesn't mean there isn't room for improving how you decide to take the shot technically, but to pass over the subject because someone else might think it mundane? Bad idea. You said you walked around the place for half an hour or so I think and this was all you found. Then that's the story - your story of that day in these photos. Look, I enjoy a beautiful flower, tree or sunset as much as the next person - nature is a marvel to us all - but there's such a homogeneity of subject matter in these photos that they become easily passed over, tuned out.
I found your photos interesting because you included something unusual... something about the life we all experience (trash can), a bit of a different take on the beautiful (a run down fence juxtaposed with the gorgeous sky), and the human interest bit because it told your story of your walk around this place that day.
Seriously, don't listen to anyone tell you what to shoot. That's your call. As for the technical side? I'd soak up all you can - they know some stuff.