My understanding is that Ren'Py is based on Python, and speaking as someone who picked up Python over a one-week period that wasn't even particularly intense... it isn't that difficult. If you're doing any coding at all rather than simply feeding Ren'Py what is functionally a script (as in stageplay), you'll probably pick up real python without any issue. If you're not, it still isn't a bad language to start with.
Besides Python, there's free engines like Godot (look at Rakugo Project), or other languages. To the end user I'd be surprised if the engine mattered in most cases - mostly people want standard features (save/load, show text, show sprites, special effects, maybe a gallery, et cetera), but it's not like those matter if the story they support isn't any good; besides concerns about whether you can truly own something where generated code was present somewhere in it, avoidance of slop (which your work certainly isn't) is probably the primary reason for aversion to generated stuff. People dislike asset flips for similar reasons.
So I think, regardless of engine, you'll be fine. Hopefully you'll find something you're happy to use going forwards, if you do look for other engines, though.
It's a shame that the Ren'Py dev only deigned to mention the use of copilot recently. Github now shows if copilot contributed to commits, or something like that, so it may not entirely have been a willing disclosure.
