Yoast taking over my WordPress title tag [closed]

That’s not what the SEO title does/is for. It appears that you’ve used the wp_title() function in your template by mistake.

wp_title() is intended for use in the <title> tag in the <head> for setting the browser tab/document title. However, since WordPress 4.1 this has been superseded (but not officially deprecated, yet) by add_theme_support( 'title-tag' ), so these days wp_title() really shouldn’t be used.