> LibreOffice is slow. On a ~2010 business-class Dell laptop that still is in perfectly good physical condition, running Debian 9, with a handful of tabs in Firefox and a mosh running:

Libreoffice is monolithically designed, as shouldn't be representative of the generic performance of modern software.

The reason is that StarOffice was envisioned as desktop environment, therefore, all the components of the suite are loaded on the first startup.

  $ libreoffice --writer &
  $ time libreoffice --calc --terminate_after_init
  
  real	0m0.104s
  user	0m0.016s
  sys	0m0.008s

If anything should be compared, then Microsoft Office should be used, as it always had a very fast startup (AFAIK, due to components preloading).

I think the article is very misguided; the problem is in the expectation that anything should be faster, even in contexts that are implicitly slower (networks, i.e. internet), or with features that will inevitably slow down the experience (e.g. browser plugins).

Using as reference the slowest software - Libreoffice, Atom, Firefox - is nothing else than cherry-picking.

In this perspective, a sibling article is correct - if you want faster alternatives, you have them.