Steam reviews is more similar to rottentomatoes than to a normal scale of reviews because it is just based on 2 options (like or not).
There's more to appreciation of a game than its defined parameters / flaws as a software and the experience it gives to any user hugely depends on what you're looking for in terms of emotions, mechanical requirements if any, and another whole bunch of variables. Knowing that review bombings are a thing in the back of one's mind helps with having a bigger picture of what is on display when you peruse through Steam reviews.
What I like to do basically is to focus on the really negative ones and see if said reviews are genuine. If a particular set of problems is described I will then look at patterns in order to establish a verdict on what appears to be the real issue at hand, while knowing that the pc park itself is varied enough to quite possibly not have the same issues from one user to another.
Now, you also got what you describe as the rotten tomatoes effect and I couldn't agree more, because the site itself is based on a fundamental, baseless logical fallacy which has ZERO VALUE whatsoever, that I cannot seriously take in consideration.
Basically "steam reviews are at 62%" is absolutely not enough in its own right. Its a huge baseless comfort zone meant to equaling an average of sentiments toward a definite verdict when you take it as is, since after all, its an user "global" review system. Which isn't a definite truth. Basically garbage