This is often a problem. One I struggled with often and in some cases can never be solved. It depends on who you are working with really. It isn't to say you are right and they are wrong (or vice versa), though you must think of the user and their expectations.
Here are a few of the ways I would try to teach some of my colleagues into the less is more:
- If this feature was removed entirely from the page, would it make it unusable? If the answer is that it can continue to work, then it must not be necessary.
- Is this a feature that our competitors have and are using it as one of their primary selling points?
- Does this feature bring in additional revenue? Can it bring in revenue?
- If the feature is removed tomorrow, what would users say? Would they notice?
- If you have data for that feature. How many people are using this feature? How are people using this feature?
- When we perform updates, how much additional time must we take to update this feature?
The big problem with many of the products launched is that they simply have too many features. It is difficult for users to understand what the intent of the product truly is. The idea is to put up the minimum viable product (MVP) and improve upon that. In time the product will morph and that is to be expected. Though at a core the user must be able to understand and even be able to describe the core of the product.
Unfortunately I was unable to properly voice my opinion that we had too much in many of our products. Though the product itself was really nothing more than 3-4 core features, we launched with over 35 features. The marketing for the product was complicated, the new user experience was confusing (tutorial), and users couldn't quite get what the product was trying to accomplish for them (what problem are you looking to solve?). In the end the product failed. I took it and relaunched it with the 3 core features, heavily simplified and people got it. Marketing was simple and then we had a lot to work with.
Less is more solves a lot of problems, not only for your users.