Apple;'s hardware and software changes quite rapidly,
so many of us groan at the changes /adjustments.
Seems we just have to "play" it Apple's way ... when our old ways of working change:
Thankfully, expert guidance is provided online, from Apple supports articles / User guides..
Eg:
"Make and play a slideshow (including videos)
You can create a slideshow to view a collection of photos and videos that you choose from your library. Slideshows are automatically formatted and set to music.
- Tap Library, then view photos by All Photos or Days.
- Tap Select.
- Tap each photo you want to include in the slideshow, then tap .
- Tap Slideshow from the list of options.
- To change the slideshow theme, music, and more, tap the screen while the slideshow plays, then tap Options.
Note: You can also make a slideshow from an album. Tap Albums, tap the album you want to create a slideshow from, then follow the steps above.
Complete article: https://support.apple.com/en-au/guide/iphone/iphd01c01cb0/ios
All the best :-)