Hardcoded `width` and `height` to Wordpress image functions is INSANE! This is my current sollution to the problem, that removes `hwstring` and keeps `srcset`, `sizes` and other responsive image attributes.

Wordpress: Remove hwstring from images (and keep srcset)

<?php
class Picture {
	
	public function init_remove_hwstring() {
		add_filter('image_downsize', array($this, 'remove_hw_from_downsize'), 10, 3);
		add_filter('wp_get_attachment_image_attributes', array($this, 'add_srcset_sizes'), 10, 3);
	}

	public function add_srcset_sizes($attrs, $attachment, $size) {

		$meta = wp_get_attachment_metadata($attachment->ID);
		if (empty($meta['sizes'])) { return $attrs; }
		
		// Srcset
		$def_width = false;
		$srcset = [];
		remove_filter('image_downsize', array($this, 'remove_hw_from_downsize'), 10, 3);
		foreach ($meta['sizes'] as $size_name => $data) {
			$def_width = $size_name === $size ? $data['width'] : $def_width;
			$srcset[] = \Cibulka::Base('WP_Utils')->get_image_url($attachment->ID, $size) . ' ' . $data['width'] . 'w';
		}
		add_filter('image_downsize', array($this, 'remove_hw_from_downsize'), 10, 3);
		$attrs['srcset'] = implode(', ', $srcset);
		
		// Sizes
		$attrs['sizes'] = sprintf('(max-width: %1$dpx) 100vw, %1$dpx', $def_width);

		return $attrs;

	}

	/**
	 * @link https://wordpress.stackexchange.com/a/29886/28718
	 */
	public function remove_hw_from_downsize($result, $id, $size) {

		if (!wp_attachment_is_image($id)) {
			return false;
		}

		$img_url = wp_get_attachment_url($id);
		$is_intermediate = false;
		$img_url_basename = wp_basename($img_url);

		// try for a new style intermediate size
		if ($intermediate = image_get_intermediate_size($id, $size)) {
			$img_url = str_replace($img_url_basename, $intermediate['file'], $img_url);
			$is_intermediate = true;
		} elseif ( $size == 'thumbnail' ) {
			// Fall back to the old thumbnail
			if (($thumb_file = wp_get_attachment_thumb_file($id)) && $info = getimagesize($thumb_file)) {
				$img_url = str_replace($img_url_basename, wp_basename($thumb_file), $img_url);
				$is_intermediate = true;
			}
		}

		// We have the actual image size, but might need to further constrain it if content_width is narrower
		if ($img_url) {
			return array( $img_url, 0, 0, $is_intermediate);
		} else {
			return false;
		}

	}

}