Yes, but the means of said balancing is not always clear
The Force being in balance has been a running theme since the very beginning. Lucas drew inspiration from Eastern philosophies like Zen Buddhism and Taoism, in which balance is a large factor. So, in that regard, yes, The Force will always try to balance itself, since out-of-universe, that how it was created, and therefore, in-universe, thats how it is.
Lets establish a bit of context as to why The Force tries to balance itself1. If we simplify the Light and Dark side to Order and Chaos, it is easier to understand. If you have too much Order, nothing changes. If you have too much Chaos, nothing can be.
The Jedi strive to protect and preserve everything, and so can pull The Force out of balance with too much Order. The Sith, on the other hand, strive to bend The Force to their will, and take its power into their own hands. This tends to lean too close to Chaos.
When either of these happen, The Force corrects for it. On a Macro scale, we can see this in the fall of the Jedi. They had held the galaxy in stasis for almost 1000 years, so the Sith overthrew them. Then the Sith went power mad and wrought too much destruction and The Force had to correct again.
On a Micro scale, we can see the same thing play out with The Ones in the Clone Wars animated show. We see them in Overlords, Altar of Mortis, and Ghosts of Mortis where they have almost absolute control over The Force, and by extension, their world. Which is why The Father chose to sequester them on said world. Without going into many details, it is there that The Son (who had inclination towards destruction) and The Daughter (who was inclined to preserve) were both kept in balance by The Father.
Now, to get back to the question at hand, you outlined a scenario presented in The Last Jedi, and asked if The Force always raises someone Light/Dark to balance someone Dark/Light (and if so, where is Snoke's equal). And the answer is... kinda. The act of balancing sometimes manifests as an individual person with the power to affect change. Sometimes not. In current canon, it is almost exclusively this method. However, Anakin's birth is an example of a time where The Force was altered so drastically, balance naturally occurred without a person bringing it to fruition2.
Its worth pointing out that The Force is not always in balance, but tends to swing back and forth in a constant attempt to correct itself. And this takes time, so there will not always be a match for a certain Force user (in this case Snoke3). I imagine that Episode 9 will round out the current arc and show up the completion of this rebalancing.
To wrap this all up, balance is not necessarily the "light-side" having as many equivalent users as the "dark side". And error correction takes a bit of time to occur.
1 - While slightly outdated, this answer does a good job talking about balancing The Force (though in context of The Chosen One).
2 - This was more fleshed out in Legends and is less clear in current canon
3 - Though if we are being honest, how powerful was he really given the ease of his death?