Yes you can copy art and crafts as a personal exercise to improve, you just can’t sell, publish or pass it off as your own work.
I’m surprised the vote is currently a small majority saying the OP is unreasonable. Commercial considerations aside, it’s just dishonest; taking credit for someone else’s talent and labour.
For most arts, craft, design and scholarship it’s not the physical ability to create the end product that has the value, it’s the idea, composition and design. I can write and type, that doesn’t mean it’s okay for me to type out an Emily Dickinson poem and share it on Facebook as my own work. I’m not as gifted as Emily Dickinson because I can write out her poem. That’s an extreme example but a real life one is that I’m currently copying Cezanne, Gauguin and other similar artists works in oils to help me be more expressionistic and hopefully learn from how they apply paint and colour and simplify and suggest form and light. I also paint from life. Now I’ve painted a belting Gauguin still life, even if I say so myself, so much more effective and energetic than my paintings from life are, and that’s because I’m not as fucking good as Gauguin! When I’m not slavishly copying his marks, composition and colours, I’m back to being an unremarkable hobbyist.
Can’t people see why it would be wrong for me to post photos of these copies without acknowledgement of them being copies? Let alone selling them.
At least Cezanne and Gauguin are dead and wouldn’t be missing out on income as the people currently creating things to sell do. Imagine the frustration of coming up with something really effective and getting the affirmation and income from reviews and sales only to see 3 other sellers undercutting you within weeks.
Yes you can’t stop someone cross-stitching a crinoline lady because you’ve done one, but you CAN stop them producing identical patterns or copies and passing them off as their own work or selling them without permission.