It's hard to describe, really. The best way I can put it is that things happen in Ducktales but I don't feel emotions as a result. It's very bland and stale.
Like, you know how Amphibia makes you feel feels multiple times throughout the first season? Whether it's when the whole town rallies to Anne's side during "Toad Tax," or when Sprig stands up for Anne against Sasha in "Reunion"? Ducktales never arouses any emotions in me like those moments did. Even the big, important moments in Ducktales are just kind of bland and flat and underwhelming. The big climaxes, the huge twists, the heartfelt reveals, there's no feeling to them, no passion, no joy or shock or sorrow.
I'm not invested in Ducktales and it doesn't entertain me. This is why I basically don't watch it, I just catch the occasional episode. I feel nothing for the characters and the plot doesn't interest me. I can tell there's a lot of effort put into everything going on, but it all feels fruitless and useless. Amphibia makes me feel emotions and excitement for the characters and what's going on in the episode, but Ducktales doesn't. I can't go into much more detail since I don't quite understand just why Ducktales fails and Amphibia succeeds. I just know they're both what they are.