I have to say that I am having the same issue. My catalog loads just as sloooooow as agclarke. I have 700 products in 4 categories, With WP version 4.8.3, PHP 5.6.30.
Here is the link to the catalog: https://gratefulhippie.org/charity-shop/
I have tried all of the above suggestions, I am afraid that I must not know what the “excluded_layouts” does. I get that it does not load the layouts selected, but it appears even with the code added, the others still load. How would I know, if its working, or not as the case may be
I have tried everything from removing all other, widgets, plugins, changed templates, even altered so that only 3 products are shown at a time.
Absolutely nothing else on my site loads so slow, but for the catalog.
I would certainty welcome ideas to resolve this load time, if anyone has any.