I use Firefox as my web browser of choice. I also tried it on Edge and it also seems to run slow on my PC. Maybe it's a specs issue.
I wouldn't know exactly how I would solve it haha, it's not my game after all. One thing I thought of is that you could keep the mechanics as is, but just give it a different visual representation, kinda like interpret it in a different "theme", rather than a 1-to-1 representation of a visual programming language. I think what could be interesting is that instead of representing the node as having if-else statement etc., you could make it like a bunch of geometric shapes, and each shape represent a different "programming functions". The virus can link to different shapes, and you have to configure your virus to have those shapes to link to them, exactly how real virus behave, where they binds to specific molecules based on their specific genetic shapes.