Should maximum simplicity dictate success?
We all love usability these days right? "User experience is important."
Of course it is!
But, it doesn't mean that every user you show the design to is going to, or should immediately be able to, understand fully what you're showing them.
Most valuable things in life take a little investment/effort. Your dashboard can probably push boundaries and comfort zones a little bit as well, especially if it's a service that will have somewhat repetitive use by your users.
Before I continue, I will caveat that this advice is for largely operational dashboards, used somewhat regularly, and for people looking to take action on insights.
I'm not advocating for sloppy work, or making your dashboard needlessly complex. However, don't necessarily design with a goal of making the first impression as easy as possible. There is only "1" first time UX; but there will be many more "Nth" time uses of your service, right? As such, if you're designing primarily with the "Nth" visit in min, don't necessarily expect that users will understand everything on the first viewing. It is possible to design a high quality dashboard that doesn't necessarily get great user feedback on the first viewing.
Also, if the user hasn't put in a little effort to understand the value of the data/information you're showing, and you've done a good job presenting it as elegantly as possible, then don't necessarily water the design down to accommodate the newbies. It may be ok as-is, and you can set up your test plan/protocol to validate whether you've pushed it too far, or done a good job of providing rich information density that is relevant.
For many of my clients, their assumed path to dashboard simplification is "remove stuff" and use "drill down" to provide detail. Don't get me wrong; I love using subtractive techniques over additive ones when it's the best choice, but there are times when you need to add data to increase the value and insights. The drill down may not have the "summary" information that is helpful in knowing whether you should even *bother* to drill down.
As a product or analytics leader, your job is to find the balance between too much/too complex, and too simple or too low in information density. There is no single clear cut definition of what too much / not enough looks like, but don't just focus on concern around the design being "too complex." You might be making it "too simple." It's possible to design a product/service that is super easy to use, but with very low value or utility.
Maximum value, on the other hand, is obtained when an analytics solutions has the trifecta of utility, usability, and beauty/desirability. It is hard though, and usually quite expensive, to get a service to that level without intentionally designing it to be that way.