iOS 18 beta Photos app is one of the reasons that I would want for Apple to allow downgrade even after many years have passed...
I have switched back to iOS 17.6 [despite saying in the past I would skip iOS 17.x] because of the unnecessary changes they made in iOS 18 beta and it's been almost a week since I downgraded... Every new major version they release, the more that iOS is getting unrecognizable from what it used to be, from what it used to look like...
Yes for now you can still downgrade to iOS 17.6 but once iOS 18.0 is no longer beta, iOS 17.6 [or any iOS 17.x update] downgrade will only be available for a limited time... What if Apple never reverts Photos app back to its pre-iOS 18 beta form, not only will you be unable to downgrade but you will be forced to like the Photos app or use an entirely different app for managing photos and videos...
I'm not asking to have every version released to be re-signed or allowed for downgrade [in iTunes or Finder] but just the final update of every version, iOS 16.x, iOS 15.x, iOS 14.8.1, iOS 13.7, iOS 12.x, iOS 11.4.1, iOS 10.x, iOS 9.x, iOS 8.4.1, iOS 7.1.2, iOS 6.x, iOS 5.1.1, iOS 4.x
Once Apple allows downgrade to versions several years ago, then some very old devices will be able to have very good speed and performance at the cost of security and new features...
I still have a working [pre-owned] iPhone 4 and iPhone 4s that I would like to downgrade to iOS 4/5/6 and just use for basic calls and text, and I think iMessage and FaceTime would still work on those old versions...
Now that Apple finally switched to USB Type C from Lightning, the EU should focus next on allowing iOS/iPadOS downgrade as part of right to repair...