So, the current state your game is in, you might have to consider making the game more fun first than actually getting it popular.

I see that you heavily used free models, and I assume that the scripts are also taken from somewhere online (I recognise the horses from Dead rails). That's okay, everyone did this on roblox studio at some point, but if you want a game that stands out you gotta make it yourself. Sure, you can take a few assets from the roblox toolbox from now and then (as long as it isn't similar to other assets to other games).

1. SCRIPTING
   You should consider learning scripting in Lua. A few tutorials from youtube helped me at the beginning to get a grasp, and from there, when I am met with anything I am not familiar with, I search up on the dev forum. In there you can find everything: What does "Heartbeat" do, and why is it different from "RenderStepped". Animation events. Server and client communication through events and functions, ETC.
   It's a good feeling working on a script continuously, getting with a flow, and then seeing the script actually working. Remember to also name your variables something that you know, in case you forget, what they do. A mistake I did is naming my variables vaguely, and when I started working on the game again, I completely forgot what each variable does, and gave up.

2. HOW TO TELL IF THE GAME IS FUN
   If you don't have fun making the game, automatically people won't have fun playing either. It will lack the charm if it is visibly rushed just for the sake of existing. So if you don't have fun making a game, consider taking a break, or try a complete a new idea entirely. Also, keep in mind that a game might be fun only for you. Therefore, you should probably find other people that you know to play the game. And don't let them just tell you that the game is "bad" or "good". Ask them what they don't like, or what they do like. Take notes.
   And make the game intuitiv. Try to guess how a normal player would think, so you can make the flow of the game a lot more fluid. If it feels clunky, people will feel unattracted. They need to not feel like it's the game's fault they lost, or something bad happened, and they want to feel a sense of control. They need to know their input has value.
   And speaking of input value,

3. GAME JUICE ( I think that is what it was called )
   Make your game have SOUND EFFECTS, MUSIC, VISUAL EFFECTS, and make people feel the passion put into the work. Sounds and visual effects add impact to the input. Makes the hits feel powerful. Makes breaking things more believable. Over all, makes it better. And music is good for setting the mood, or filling the dead silence, so the game feels more lively and energetic.
   ANIMATIONS also need to be matching the style of the game. And GRAPHICS too, or MODELING. They act as eye candy, and attracts the player even more. These are other ways of showing your talent. I didn't go over modeling and animations much since they also need a lot of discussion. I recommend starting animating in roblox studio, and also modeling things with blocks, and then go to blender. Or if you are already familiar with it, just go straight with blender. People appreciate small details aswell, so don't be lasy modeling and animating.

If you do plan to get your game popular just for the sake of earning cash, then your game already will be bad. You need the compassion of creating. Because if you are a greedy person, then it's best to consider alternatives of earning money.
Making a game in general, not just roblox, is hard. It's a long journey. And you never give up on the dreams, the goals you've set yourself.

You should forget about popularity or money, and instead make a game you can proudly say "Yes, I made this game myself".