Isekai like Leadale offer the protagonist a second chance when their previous lives are filled with disappointment or in Cayna's case, pure tragedy. Even before her death Cayna's life had ended before it could begin which put her in a more unique position compared to other isekai protagonists or even compared to other "Players" that ended up in Leadale. Her "reincarnation" into Leadale allowed her to live a life she could not have dreamed possible back in the hospital bed where she was once imprisoned. But while Cayna seemed to have the life she never had the other characters weren't in those positions which raises some big problems with the show as a whole.
Leadale is a mediocre isekai fantasy. There is no denying that. But the problems with the show as a whole come from the distinct lack of direction for the plot.

Why did the players get trapped in the bodies of their video game avatars?
How did the players get sent to Leadale?
What are they going to do about this?
Where are they going to get answers to these questions?
Who was responsible for this?

The driving plot for Leadale is Cayna activating the Guardian Towers that have been abandoned after 200 years since Leadale the Game was shut down. Okay. Nothing too remarkable but it's a start. Its a goal for the main character. The problem is there is no reason why beyond Cayna is bored. Will activating the towers magically give us the answers to those questions of why and how all these people ended up trapped in Leadale. Can they use the towers to contact someone who can help them? We don't know. There are no answers or hints given at any point during the 12 episodes. But its okay because no one seems concerned.

Aside from the lack of a concrete plot, the characters are what makes and breaks Leadale as a series. Cayna is a problem character. Hot and cold. Psychotic and motherly. She is constantly bouncing between two if not more personality traits like a game of ping pong. It seems that the author couldn't nail down a personality for her so instead borrowed the traits of other isekai protagonist from across various series instead of making one from scratch. Her chaotic personality theoretically should have been enduring or funny but is neither and instead comes off as deranged and broken.
The side characters are where Leadale shines. Lovable and funny the NPC's are the heart of the show and the world of Leadale. The other player characters are more complicated. While they are far improvements from Cayna, they lack drive and agency. Not once did any of them seem concerned or question how or why they ended up on Leadale. Years of their lives lost in this other world that they randomly found themselves in and they seem fine with it. Acceptance is a worthwhile trait to have since dwelling on the past won't get them anywhere, but they act like they don't even care at all about what they lost. 2, 3, even 10 years they were trapped there without answers and those answers are what they and the audience deserve. Cayna shows up, who is probably the one person who could possibly have or be able to get answers or call for help, but the thought doesn't cross their minds to ask. This makes their characters incredibly shallow and no different from the NPCs. It's painfully frustrating to watch these characters ignore what happened to them and settle for a state of ignorance and basically ignore the problem. Having them question how they ended up in Leadale or how do they get back home, would give them more agency and significance as characters beyond just appearing and disappearing on and off. Expressing some thought or feeling about their situation no matter what it is would give them much needed depth. Happy, Sad, frustrated, content? This ties back to the lack of direction for the plot.

All in all things in Leadale just kinda happen. There is no driving narrative, only this happens and its easy resolved so another thing happens. There is nothing really connecting the events together to create a cohesive narrative. Its all the whims and desires of the author without a plan. I think Leadale would improve far beyond mediocrity it did have a more driving force behind Cayna's actions like trying to get the other players back home or even finding answers. The show is like Cayna, constantly shifting between light and dark and just doing whatever it wants to because there is no one there to guide it. That ultimately hurts it in the long term.