This is entirely your choice of course but I genuinely can't look at your site for more than 5 seconds and read anything due to your background gif. Perhaps you can use a regular still image of the same effect?
I agree, the default full background animation is
really hard to look at and hurts my eyes. I think it could trigger migraines or seizures due to the rapid flickering of the white parts of the static- I messed around with the tile size of the background, and making it larger didn't help but making it VERY small (1%) did. It still hurts to focus on the background, but it's a bit easier to ignore at that size, making the rest of the site at least readable. I see you have a splash page (your "enter" page)- if you want to keep the animation, I'd put a warning for rapidly moving images.
I didn't realize until poking around on your site that the big pink button is actually a toggle for the background! You may want to make this more obvious, or at the very least reverse the order so that the default theme is "light" instead of "dark".
I think another alternative for readability's sake, if you wanted to keep the animation, is just reducing the area that the static is displayed. Instead of having a huge chunk of your background display static, keep it in the borders of your divs. I think this looks nice, though it may not be what you're going for (u_u)
Here's a mockup:

I added this to your section and headers
border-image: var(--bg-image) 10 repeat;
border-width: 10px;
border-style: solid;
That's pretty much the only critique I have though, the rest of your layout looks great!