I stopped using PowerPoint for presentations long back. What I use now is LaTeX with the beamer class to make classy professional looking presentations. This looks like another good alternative to try out.
You might also like "marp", which works as a VS Code plugin for markdown. Much simpler & less control than Beamer, but does allow equations (which it seems the linked presenta.cc does not, or not yet) and a bit more off-line focused perhaps?