The View Transitions API is now over 96% support, so is production-ready.

Why CSS-only? – it ensures it works reliably with other WordPress plugins & other custom functionality without requiring custom code (re-initialising JS functions etc), which is often required when using JS libriaries like Barba / Swup to simulate page loads.

Importantly, with CSS-only the page load is preserved and allows the to browser handles the transitions between pages.