Invision Community 4.7.3 is going to remove the guest page cache which was really a very old and bad technique.
A much better and modern approach is a real cache engine like Cloudfront or Cloudflare.
To set up the caching of the IPS pages with Cloudflare, go to your Cloudflare site settings and open the "Cache Rules" page.
Create a new rule and set following expression:
(not http.cookie contains 'ips4_member_id' and not http.request.uri contains 'login' and not http.request.uri contains 'register' and not http.request.uri contains 'api' and not http.request.uri contains 'admin' and not http.request.uri contains 'contact' and not http.cookie contains 'ips4_IPSSessionAdmin' and not http.request.uri contains 'terms')