I have a Magento 2.3.5 installation with more than 40,000 products and 5 store views. The page load of any category is more than 10 seconds. I've found that this function takes between 0,08 seconds and 0,1 seconds:
$productImage = $block->getImage($_product, $imageDisplayArea);
It's inside the file: vendor/magento/module-catalog/view/frontend/templates/product/list.phtml
So, if I have 81 products to show (like me), it takes more than 10 seconds to load (0,09s x 81 products=7,29seconds).
Why does it takes so long that function?