There's some good feedback in this thread. Sebastian, in particular, is nailing some of the issues. He's giving specific technical feedback, however, and I tend to try to aim for a simpler system that's going to handle the details without you having to learn as much. I run a web design & hosting company and have built about 200 Wordpress sites so, while I'm still a newbie on permaculture, perhaps I can add a bit as well.
Building a website that's going to deliver both high and low bandwidth options well is a considerable headache. My recommendation is to build a website that's streamlined from the ground up for relatively low bandwidth. Let people who are on slow connections customize their browser settings to throttle the content as necessary. Many won't know how to do that - but that's something you might think about researching and adding to your website.
What makes a website fast?
Theme selection. There are really good/light ones like https://sepalandseed.com but your theme seems pretty light as well./Plugins. Limit them as much as possible. They all add up.Images. You're optimizing yours to some extent, but still have 1.7MB of images loading with your homepage.Content/architecture. Long scrolling pages make for easy browsing for many people, but are bandwidth hogs.Hosting matters. Dedicated hosting isn't necessary, however. I run dedicated servers for my business but deliver many websites off the same servers. As long as your shared server has adequate resources, it should perform just fine.CDNs - content delivery networks - can greatly speed up delivery of websites, depending on configuration and location.
Check out https://tools.pingdom.com/#5a029c05bd800000
for another view of your site, speed and content. Your images seem like the biggest current bandwidth issue and your theme/plugins and the flies they load are the second thing I'd look at.