What makes a simple browser game feel genuinely replayable

I have been building a lightweight browser game and something I keep thinking about is how much replayability matters when you are working with very small mechanics. Some games with only two or three actions somehow keep people coming back, while others with far more features lose attention fast.

For those of you who have launched or tested small interactive products before, what do you think actually creates that loop that makes someone want to try one more round

Is it speed, progression, randomness, difficulty shaping, or something else entirely

I would really like to hear how other makers approach this, especially since more people are experimenting with small web based experiences again. Here is the version I am testing right now if you are curious to see what direction I am going:
https://wordsus.app

Would love to know what elements you personally feel make a tiny game stick and what usually makes you bounce off.