But your issue is not so much a “theme issue” in the sense that there’s something wrong with the theme: the logo and tagline are exactly where the theme’s author intended them to be, so there’s no “theme issue” in that sense ??

Of course, you can override the theme author’s intentions and centre your logo and tagline if you so wish. Except the CSS code you have in your screenshot have nothing to do with centring elements on a page!

So if you want to centre your logo and tagline, with the tagline BELOW the logo, follow these two simple steps:

STEP 1: Remove the following custom CSS you place in the “ADDITIONAL CSS” box of Customizer:

.site-description {
    width: 2000px;
}

.site-branding {
        display: table;
}

STEP 2: Add the following CSS code instead.

.site-branding {
flex-direction: column;
}

Good luck!