Welcome to the community. 
All trainers need to be voted for in the WeMod desktop app. Trainers aren’t made unless the community tell us they want it enough.
Bear in mind, the game was released in 2013. Most people who wanted to play Grand Theft Auto V while it was still “in fashion” already own the game from Steam or on consoles. Or Epic Games (where it was given away free - [Free Game] [Expired] Grand Theft Auto V).