Hi! I think the "amateurish" feeling is less about one bad element and more about the UI system not being strict enough yet.
What stands out to me:
- The fantasy title font is strong, but it is doing too many jobs. Buttons, small labels, numbers, shop text, and headings all have similar visual weight, so the eye has trouble knowing what matters first. I would keep the decorative font for titles and primary CTAs, then use a cleaner readable font for small labels/prices/body text.
- The gold/brown border treatment repeats everywhere at almost the same strength. Level cards, shop panels, inventory slots, buttons, and HUD boxes all compete. Pick one "primary panel" style, then make secondary cards thinner, darker, or lower contrast.
- Alignment feels loose. The menu buttons, level cards, shop, inventory, and confirm button do not feel like they come from the same grid. A simple 8/16 px spacing system would help a lot.
- Some contrast is too low: "No penalties", item prices, small level notes, and disabled buy buttons blend into the dark background. Push important text brighter and make disabled states more obviously disabled.
- The icons feel like different icon sets. Coin, scissors, chisel, gear, and tile symbols use different rendering/line-weight languages. Redrawing or recoloring them into one consistent silhouette style would make the whole UI feel more professional fast.
Quick fix I would try first: reduce the floating background shapes behind menu/UI screens, brighten the panel fill slightly, thin the secondary borders, standardize button sizes, and reserve the fantasy font for title/primary actions.
The base art direction is solid. It mostly needs hierarchy and consistency, not a total redesign.