Overall, I think the game has a lot of potential during my review. Personally, I would like to see more humanoid Pokémon, as it aligns with my preference. Additionally, I believe adding more content would enhance the experience. In terms of difficulty, I find it adequate. Roxanne defeated me once with her Minior, but after realizing its presence, I easily overcame it with work up spam on Geodude. However, I do agree with the concern about money in the game. One way to address this could be by including repeatable trainers or adding more trainers to battle, which would allow for faster grinding and experience gain to lower the overall difficulty. For example, you could reward players with 1,000 units of currency per battle against level 12-15 Pokémon after defeating Roxanne, and this scaling could continue after each gym leader.
Another improvement I suggest is making TMs reusable. This change would offer more team variety and reduce difficulty for weaker Pokémon. Regarding the game's art, a temporary solution could be incorporating generic rule 34 art in certain areas to maximize visual diversity until original art is added. It may require minimal effort to search for trainer-related artwork on rule 34.
I'm particularly excited about the inclusion of shadow Pokémon in the game. Furthermore, a feature that could be considered for future development is allowing players to breed their Pokémon or the trainers' Pokémon. This addition could generate extra income and provide additional content for those interested, although I understand that it may not appeal to everyone. Regardless, I encourage you to continue your great work, and I eagerly anticipate witnessing Ralts's evolution.
Keep it up.