Sure:

- images: none are visible above the fold - all should be lazy loaded (like it is done with all conference images) and the pragdave.jpeg one does not need to be that large;

- JS: navigation toggle, including chevron rotation can be done in CSS using :has combined with checkbox/radio input. Similarly for header-navigation and theme-toggle (here combined with cookie store). Then toc.js - seems like something easy to do in the backend. Hero-animation - I haven't looked much through it but seems like at least some parts can be done in CSS;

- CSS/tailwind - well it would probably take less typing to do it just in CSS, the site does not seem to be that much componentized to benefit from tailwind.