2019 Mazda CX-5 brake fluid flush at 40k miles?

Not an upsell, but it is not really about the miles either. Brake fluid is hygroscopic, so it absorbs moisture from the air through hoses and seals over time. That water lowers the fluid's boiling point and starts corroding calipers, brake lines, and the ABS module internals. The standard service interval is every 2 years regardless of mileage, because time is what ruins the fluid.

On a 2019 CX-5 at 41k miles, the question that matters is when the fluid was last changed, not the odometer. If it has never been done in 7 years, it is genuinely overdue and you should do it. If it was flushed 2 years ago, you can politely decline and wait for the next round.

Brakes feeling normal does not tell you anything here, since moisture contamination does not change pedal feel until the fluid is badly degraded. It is also not an emergency, so do not let anyone rush you at the service counter. Your CX-5 is spec'd for DOT 3 fluid, and any good independent shop can do the flush for less than the dealer.

My take: at 7 years old with no prior flush, do it, just get a second price first.

https://ezcarfix.com/blog/brake-fluid-flush-when-and-why