slide show
How do you display photo titles in a slideshow?
MacBook Pro 13″, macOS 12.6
You have to add them manually to each slide in the slideshow.
Click on the ⊕ button at the right end of the slide tray and select Add Text for each slide.
There is another way to get a slideshow with titles but it's done with an AppleScript: Script: A Slideshow With Titles and Locations And Dates in Photos. You can edit the script to remove the locations and dates.