The WordPress theme for 2019 is a clean, minimal theme with a beautiful layout. It arrives out of the box with a depressing blue overlay over every image. Luckily the latest update includes a customizable site color that controls the overlay color. It does not have an opacity setting so here is the code to customize your featured images:

.site-header.featured-image:after {

background: #000;

transition: opacity 1200ms ease-in-out;

opacity: 0.5;

z-index: 5;
}

Just add this code to your custom/css options in the WordPress customizer dashboard.