Check your battery health in settings.

iPhone 11 is approaching five years old, and Li-Ion batteries don’t have an endless lifespan. Especially if you let it get below 20% frequently. I wouldn’t be shocked if your maximum battery capacity is pretty low, and that’s just normal wear and tear.

You could probably replace the battery at an Apple Store or certified repair shop, which would essentially make it behave like a new iPhone 11.

There were some battery drain issues in iOS17 related to specific apps, IIRC, which have since been resolved.

The thing Apple got sued for was sort of the opposite of increasing battery drain: slowing the performance of the phone to prevent it from shutting off while still having battery capacity. Phone battery draw isn’t smooth, it’s spiky, and they were dealing with a defective battery design that didn’t have a properly predictable voltage curve. So occasionally the CPU would require a voltage the battery couldn’t provide and the phone would turn off, even though the battery had plenty of juice. To prevent these shutoffs, they underclocked devices with older batteries.

The problem is they didn’t really tell anyone what they were doing, at least not publicly enough.