Simplicity is political, not visual
The hard part of unifying a sprawling product is never the design. It is getting many owners to agree whose priority comes first.
When people ask what makes a product simple, they describe how it looks. Fewer things on the screen, more room around them. That is the last stretch of the work, and it is the only part most people ever see.
The version of simplification I do most often has almost nothing to do with how anything looks. I take many separate platforms, each built by a different team at a different time, and turn them into one system a person can move through without knowing which office built which part. On paper that is a structural problem. In the room it is a negotiation.
On one large public-sector unification, every organisation involved wanted its section placed a particular way, in a particular position. The request that came up again and again was to put what that team considered important into the first fold. Not what the person arriving at the site was trying to do. What the team was accountable for.
All of those cannot go first. That is the entire problem, and it is arithmetic rather than taste. The top of a page holds one thing. If several owners each need their thing in it, most of them are going to hear no, and the person who has to say it out loud is the designer.
So the question in the room is never whether we can design it. Of course it can be designed. The question is whether a group of people who each own a piece will agree that the user's priority outranks their own. Nobody is being unreasonable when they push back. Each team is defending work it is answerable for, and asking them to give up the top of the page is asking them to look less important to the people who review them.
This is why I stopped calling it a design task when I talk to stakeholders. Calling it design invites the reply that it is a matter of preference, and preference is something anyone senior enough can overrule. Naming it as a decision about who the product serves first changes what the meeting is actually about.
What moves it is putting the trade on the table as a fact. Several sections cannot share one first fold. Once that is stated plainly instead of argued aesthetically, the conversation stops being about whose section deserves to win and becomes a question the group can answer together, which is what the person came here to do.
The visual part still matters, and I want to be clear that I am not arguing for plain. A simple interface can and should be beautiful. But the beauty is downstream. It is what you get to do once the harder agreement has been reached.
This is the half of the job that does not photograph. There is no before and after screenshot for a decision about whose priority comes first, which is a large part of why design keeps being mistaken for decoration. The screen is where the argument ends up. It is not where the argument happens.
Simple is not a look. It is a decision about who a product is for, made by people who each had a real reason to decide differently. The interface is only where you can finally see what they agreed to.