At least CSS animation is optional. I have the following in chrome/userContent.css in my Firefox profile directory:

  @namespace url(http://www.w3.org/1999/xhtml);
  
  *, :before, :after {
  transition: none !important;
  animation-delay: 0ms !important;
  animation-duration: 0ms !important;
  }

This also requires setting toolkit.legacyUserProfileCustomizations.stylesheets to true in about:config

As far as I can tell this doesn't break anything important. I also have the same in chrome/userChrome.css (without the namespace header), which occasionally breaks the tab bar in what looks like a race condition bug, but it's still worth it IMO.