I guess this is a matter of preference. I see when I click a link on stack.lol that the page header remains visible, but the rest of the page disappears (blanks to white) for a second before the next page appears.
I prefer a seamless experience of seeing the next page immediately without a "white flash" first. For instance, if I am looking at a GitHub project page and I click the "Issues" button, in a fraction of a second the page changes to the Issues page without any intermediate disappearance or partial page load.
In most cases, I find transition effects like fading, sliding, etc. to be an annoyance that adds unnecessary delay and visual distraction.
I believe this is related to the implementation of the light/dark theme. It uses the preferred theme but default to light, if your preferred theme is dark, it will take some time where it defaults to light before being set to dark. There are workarounds.
I prefer a seamless experience of seeing the next page immediately without a "white flash" first. For instance, if I am looking at a GitHub project page and I click the "Issues" button, in a fraction of a second the page changes to the Issues page without any intermediate disappearance or partial page load.
In most cases, I find transition effects like fading, sliding, etc. to be an annoyance that adds unnecessary delay and visual distraction.