How do I delete wasted space on my iPhone like “other”? Apple is now forcing us to buy storage, very unhappy

Update to iOS 14.4.2 (Or to the latest iOS based on the iPhone model you possess), if not done

iOS 13.6.1 --> Addresses an issue where unneeded system data files might not be automatically deleted when available storage is low

• Other: Non-removable mobile assets, like Siri voices, fonts, dictionaries, non-removable logs and caches, Spotlight index, and system data, such as Keychain and CloudKit Database. Cached files can't be deleted by the system.
• System: Space taken by the operating system. This can vary based on your device and model.

About cached files in "Other"

Finder and iTunes categorize cached music, videos, and photos as Other instead of actual songs, videos, or photos. Cached files are created when you stream or view content like music, videos, and photos. When you stream music or video, that content is stored as cached files on your device so you can quickly access it again.

Your device automatically removes cached files and temporary files when your device needs more space.

If storage on your device differs from what you see in Finder or iTunes

Since Finder and iTunes categorize cached files as Other, reported usage for Music or Videos might differ. To view usage on your device, go to Settings > General > [Device] Storage.

If you want to delete the cached files from your device

Your device automatically deletes cached files and temporary files when it needs more space. You don't need to delete them yourself.

In short --> IGNORE, if you are not convinced, Restart the device. You will see that Others Storage will reduce but total storage will remain more or less the same.

Watch the demo in the GIF below made on my iPhone 6 iOS 12.4.7

To manage “other” start here: https://support.apple.com/en-us/HT211686

You are describing your physical iPhone storage AND your iCloud storage. When your iCloud storage is full, you will be prompted to buy more storage. However, when your iPhone storage is full, you cannot buy more, you have to clear up some space on the phone. If you are uploading everything to iCloud, you can go into your iCloud settings and disable some things like music and photos to clear up some space (you only get 5GB of free iCloud storage).