I have the same problem. Bought 16 Pro 3 days ago and I can reach more than 5-6h screen time and maybe, maybe 1h - 1.5h of idle. Can't believe in these units with 8-10 screen time... not doable in my case I think.
Turned off: 5G, AOD, background apps, location services, ets. When the phone is not being used, it consumes 1% per 30-40 mins.
Spoke with Apple yesterday and they performed an online diagnosis and the tech support representative told me, that what my phone achieves is pretty decent and he doesn't think this is an issue. The diagnosis showed the battery is good, nothing is happening.
The options I have are to replace the unit within 14 days but tbh I feel this is not the unit case because before 16 Pro I had 16 Pro Max for 10 days and had the same: when the youtubers were saying they have 18h screen time, mine was 5h after 50% of battery at most.
So I feel disappointed? I am not a heavy user but I was expecting much more from 16 Pro in comparison to my 14 Pro which I was charing twice per day. With 16 Pro I think I can make one full day but without the full comfort of not thinking about the battery.