iPhone 16 battery drains fast

I also suspect the battery hogging feature of 5g is what you are experiencing as you did not have it on your iPhone 11. You will get a speed improvement in cellular data transfers with 5g, but the range is quite a bit shorter requiring much more power to maintain a connection, especially when in a fringe area. Turn it off and compare your results.

Post the battery graph at Settings > Battery along with the top 5 apps that are consuming your battery and we may be able to provide additional information. The graph that is important here is the green one and it is best when viewed with the last 24 hour option.

The batteries in our iPhone 16 models last all day and then some. They are not rubbish as you suggest. There are a lot things which can drain a battery. You may have them set to 5G Cellular all the time and the phones may be working extra hard trying to connect to a 5G Network. You may have an app which is running down the battery in the background. Those are just two examples.

Open Settings > Battery and look at what is using the most battery. From there you can make adjustments as necessary. Then Force Restart both iPhones which will kill any unnecessary things running in the background --> Force restart iPhone - Apple Support

Mine and my wife’s are both operating just fine.