Infiroad is a Japanese idle RPG made in 2016. It recieved an award on the incremental games subreddit, although as far as I know it never became well-known in the English-speaking incremental games community. I'm guessing it fared better in the Japanese-speaking incremental games community, but I don't know Japanese and thus can't check that place.
I would place this in the same subgenre as Clicker Heroes. The set of mechanics is (almost) fairly standard for games in that subgenre. Its primary innovation in that subgenre is the way in which fighting monsters is represented. In the game, there's a line with your units moving on one side and enemies standing on the other side. Through this, the game gives a far more tangible representation of progress and power than other games in the subgenre. One minute you're moving through enemies very slowly and the next you're mowing through them. It's simple but fun. My writing skills are not developed enough to describe how I feel about this game; just play it to get a feel for what it's like.
The link actually a sort of 'home page' that contains links to two versions: a WebGL-based one and one for Windows. I recommend getting the Windows version as the WebGL one will eventually stop working due to some sort of memory limitation. However, the WebGL version is good for trying the game for a few minutes just to see if you like it. Just don't take too long.
P.S. I feel weird using the term "RPG" in this context as you don't really play as any character on the screen. The closest example would be the hero character which spawns on click, but you can spawn multiple of those. But words can change meaning, and I don't really have a better term for games which take the mechanics from RPGs but not the role-playing.
P.S.S. I feel like this post is too long. Should I have made it shorter?