Character arc (aka the internal plot) is essential for a satisfying story structure. You might have tension on every page and you might follow what you think is a winning structure, but if you don’t have a character arc, your story will fail to resonate with readers. Learn the key concepts for character arcs here.
Storytelling is a complex beast. There are lots of things that appeal to readers: poetic sentences, imaginative alternate realities, sympathetic and/or courageous characters, relatable problems, vicarious experience. But at the scene level, there is really just one simple concept that spurs the reader onward.