This is about as good as you’re going to get on an iPhone without a battery case. If you need more, I’d definitely pick up an apple smart Battery Case. It adds bulk, but also a good deal more usage.
Apple has standby drain nailed, but they just do not put in the same size batteries as Android phones that are comparable size. The average Android flagship the size of the xr has 3500-4500mah batteries. Android by definition is far less optimized, so they need the extra size. A 4500mah xr would be unbeatable, but it would be too thick for most people and it would never happen.