To give an answer that isn't just people shitting / memeing over RPGM, I'll lay out the actual reasons.
Firstly, it has issues once a games scale has increased enough, over the years games made in RPGM end up getting moved to later versions of the product / other development platforms because RPGM just won't support a game of sufficient size at a given point. Which comes with the downside of the game spending weeks / months in re-development hell where the whole thing is being rewritten and everyone calls the developer a greedy thief and no actual progress gets made on the project.
While the structure makes it easy to get started, it also hampers your ability to customize your project long term, most RPGM games end up following a certain playstyle that a lot of players don't enjoy, grinding for levels, aimlessly searching for the next goal, and it's painfully slow to progress through the game in future playthroughs if you want to make different decisions, if you lose your save, or if you're just checking out the story again. Renpy etc is typically pretty quick to push through.
And then there's the stylistic dissonance. Not really an issue, more just the fact that in general rpgmaker games tend to lean towards hand-drawn art, renpy tends to use daz models, and html games tend to run real porn. Not a set in stone thing or anything, but anyone looking at the art for this game is likely going to immediately assume it's renpy.