I agree with the idea of not delivering a half baked FSE experience. But I also think it’s a good idea not to be shipping half-baked features which is why this should be postponed to WP version 6.0.

And like I mentioned it in a comment some months ago, shipping FSE within WP 6.0 also makes for a better semantic version even though that’s not the usual philosophy of WordPress, but since you are open to reinterpreting core philosophies, this one is a good candidate even if done as a one-off reinterpretation, like it happened with 5.0.