If you spend much time here you will find the majority of people are looking for MORE features so of course that will increase complexity and also the Settings for those feature. The philosophy of If it ain't broke, don't fix it.doesn't have any weight in the fast changing technology field. Those that aren't offering new features, no longer exist, the Blackberry comes to my mind. The users looking for more features are given the Feedback link to let Apple know and you can use that same link to express your view that you don't want anything to change.
Not sure what iOS version you are referring to, but much of what you have described are not new in iOS 27. We can tackle these one at a time if you wish.
1-- To find the Photos you just took, open the Photos app and tap the Library tab on the bottom. The photo you just took will appear on the bottom of the screen and will be shown in order they were taken. The option that can be changed for viewing your Library are in the link below, along with the look for viewing your Collections.
Browse your photo library on iPhone - Apple Support
Browse your photo collections on iPhone - Apple Support
2-- Not sure what you are referring to with the Autofill in the Calendar app being changed. For the Holidays you see, just uncheck the Holiday Calendar and those will immediately go away. The Holiday Calendar has always been a Subscribed Calendar where you can't make changes to the Holidays you see, there has been no change there. The good news that you have always been able to create your own Calendar with any Holidays or Events you want and for a Subscribed Calendar, you can add your own custom Calendar and subscribe to that one. There are many websites that will let you create a subscribed Calendar to be added to the Calendar app and I also included one as an example.
Use iCloud calendar subscriptions - Apple Support
https://www.calendarlabs.com/ical-calendar/
3-- NameDrop is an excellent way to add another persons contact in your Calendar and they don't see any of your Contacts. I also have an old iPhone running iOS 16 and the process is exactly the same when adding a new contact manually. Tap the plus button and the only thing on the screen is from the new contact. None of your other Contacts are even on the screen until you tap the Checkmark to approve. On the much older iOS 16 version, the only difference is the Checkmark says Done instead.
Use NameDrop on iPhone to share your contact info - Apple Support
4-- For the Hand Gestures and Strokes causing a conflict, you will need to provide more detail on what you are referring to.
5-- As explained previously, features include additional Settings. If you want help with a particular setting, feel free to ask. You don't even need to use ChatGPT, Apple Intelligence will take you to the exact location and if you have a question about any Setting showing on the screen, then Apple Intelligence will know exactly what you are looking at.