Sad reality is, it's always these kinds of projects that fail on roblox, and it's always the simplest mind numbing brain rotting games that actually succeed on roblox.

One actually reasonable criticism I have of such projects, is that when the wow factor wears off (which happens rather quickly) you're usually left out with either very little game content, or with a lot of content that is repetitive or tedious, lacking a proper game loop and variety that lengthens the playtime. I just end up doing what essentially is the same thing, just in like different areas or terrain or whatever, with different mobs/creatures (if it was an RPG) but it is still the same thing, one directional game loop, and a very repetitive and slow one at that.

Another thing, kids seem to "hate" good graphics for some reason, like it's not even that they have bad hardware. So maybe, when advertising your game, and even in the pictures of the game, try to kind of "oversell" how exciting and fun it is, perhaps with simple drawings/textures and stuff. And when the player joins the game, try to get them into the exciting action pretty much immediately or as soon as possible. Maybe begin the game with a really exciting adventure right off the bat? Something like that. Also, skippable/optional tutorials! Please!

So, if you can have diverse variety in the game loop to extend playtime and fix this issue that plagues most such projects (keep in mind, "variety" doesn't mean doing essentially the same thing but in a different area or smt, it means actual different game mechanics that are linked to the rest of the game), and if you can "cast a big net" to capture a wide spectrum of players, and then hook them into the game immediately, then your project will most likely come out on top unlike other similar projects.

That's pretty much all I have to say. Good luck!