I believe if you consider number of different templates and features of theme, the page load is absolutely fine. Also all css and js files even related to block templates are packed into a single file and download only at first page visit. which has a huge impact on better performance.

ok I appreciate the response, though in order to look at the theme more objectively I've just tested it in Google PageSpeed insights.

The Pixel Live Demo Home Page score was "46/100" "Poor"

"This page is not optimized and is likely to deliver a slow user experience. Please prioritize and apply the recommendations below."

Therefore, surely this is not a good evaluation by Google, not good for user experience and consequently not good for SEO.

It's a real concern?

With some tweak on server settings Pixel homepage get 77/100 in google page speed (desktop version), most of the items that needs more work are the things that you can improve by using third party add-ons available on marketplace, for example you can minify the html by "Minify HTML" add-on or you can optimize all images by "Image Optimizer" add-on. Also there are some other items that you can improve by some server settings.