The Last Guardian seems to suffer from performance issues on both the standard PlayStation 4 and the PS4 Pro version.
How to access smoother performance for The Last Guardian on 4K displays
PS4 Pro Review
The Last Guardian (PS5) 4K 60FPS HDR Gameplay
The Last Guardian PS4 Pro 4K vs 1080p Gameplay
This Is it. Avoided playing until now because of extremely loud fan on PS4. I'm so excited! : r/playstation
4K/60FPS] The Last Guardian PS4 Pro Tech Analysis: Prioritizing Art Style Over High End Graphics
Tip: If you play on performance mode on the PS4Pro, try letting your tv do the upscaling by forcing the Playstation to 1080p. : r/PS4
If you want to play The Last Guardian at a reasonably stable framerate, you'll need a PS4 Pro – Destructoid
The Last Guardian PS4 Pro: How To Get Smoother Frame-Rates on a 4K Screen
Why has the PlayStation 4 been so successful? : r/PS4