Best travel credit card if you mostly fly one airline?

I’m trying to simplify my setup and stop overthinking this. If you mostly fly one airline, what actually makes the most sense long term?

Is it better to go all in on that airline’s branded card for perks and status, or use something like Amex or Chase and mostly redeem with that same airline anyway?

Not really chasing signup bonuses here, more curious what’s actually been worth it over time for people who fly a lot and stick with one airline. What do you use and why?