How do you say no to a paying customer asking for custom features?

Early on saying yes to every paying user felt like the only way to keep churn low. But we ended up building so many random custom features that our main app became bloated and hard to navigate.

When a high-value client asks for something totally off the roadmap now, it’s terrifying to push back.

How do you decline custom requests without making them feel ignored or driving them straight to a competitor?