About renpy and any other such game engine: making a similar engine with web tech would be a few days work at best for a coder with business flow development experience, because these games are really simple. On the UX part the animations are simple too. The main component is extending the story, the conversations easily, and as a developer I see a shitty tradeoff. You want to find a game engine that is extendable without a coder, so you learn an engine that is made for that purpose, but has limitations, and you get to be independent off of a developer. But, you waste time, cause what you just setted up in renpy or similar with x ammount of time, and what you could not even set up in it, would be x/2, or x/3 time for the developer.
You should consider finding a developer who can make the game engine in a relatively easily learnable programming language, like html+js+css, and not waste time creating a bloated, nocode programming monster in an engine that is way too much hassle for a simple slideshow game. I hate to even call it an engine, that word should mean more. Your game is a simple, elegant, in the art style a great game, and you should be happy that it is not a complex game on the side of mechanics, and not make it a more complex stuff. I dumped the unity assets out, and could make the whole game in 1 sitting, and I am not a great coder. Why complicate things?