The feature request trap: How do you say 'no' to loud, paying customers?

Early on, every single cancellation email was treated as an emergency signal to build a new feature. Our product roadmap quickly turned into a Frankenstein monster of random buttons and settings.

When a customer tells you Your product doesn't fit my workflow it's brutally hard to decipher whether they are asking for a custom workaround that will bloat your core architecture, or if your fundamental product design is actually flawed.

For experienced founders: where do you draw the line between accommodating a high-value customer's custom request and protecting your original product vision?