>>1 in my opinion, you're not trying hard enough. I had to do college level art in highschool when I had absolute zero skill with everything but sketching. It took hours of online AND LIBRARY BOOK research. It was always slow, sometimes 36 hours of research and planning and sketching and gathering materials. But in the end, I created my own style of art, something that no one else could imitate and my work was admired by those who initially looked down on me. In two years I became confident in pencil drawing, oil painting, plaster paris sculpting, digital art, and pastel and charcoal impression arts.
NO ONE can limit your skills, but yourself.Especially in this day and age when practically any and everything is easily accessable and taught over the internet. If you slouch in a pity party all day, then of course, your art will suck and always will.
But if you actually put some of your soul into it like I know you can- research, study, and practice, then of course you can become an artist.
Skill doesn't develop over night. Create a theme for yourself, develop what that theme means to you and create future projects that fall under that theme and what medium you want to use for each project. Take an hour a day to find visual reference materials for your project, fellow artists who have done something similar, and sketching out your project. Remember to notes in an investigative workbook. Then experiment with how you want your art to come out; create a draft of your project before creating the final. Take note of the mistakes you made and how you plan on correcting them in the final project.
Do this and people will stop doubting you, but as I said, it takes time and won't occer over night.