Apple dramatically streamlined the animation library in 2016. Several dramatic 3D transitions (like "Clothesline," "Reflection," and the original "Cube" effect) were either removed or simplified. Presenters who built intricate themes in the early 2010s find those files break in newer versions.
Keep the old hardware running this legacy software disconnected from public internet networks to avoid unpatched security vulnerabilities inherent to vintage OS environments. keynote 5.3 download
If you have a Mac that never connects to the internet (e.g., a dedicated kiosk, a scientific instrument controller, or a secure lab machine), you cannot download the latest Keynote from the App Store. A standalone Keynote 5.3 download (via a .dmg file) is the only solution. Apple dramatically streamlined the animation library in 2016
Your only solution is to export as PowerPoint (.pptx) and then open that in Keynote 5.3. Be prepared for significant formatting loss (master slides, transitions, and image placements will shift). Keep the old hardware running this legacy software