Fira Code's main problem is that it tries to be a font for all programming languages which results in some weird behaviours here and there. Unfortunately, there's no good way to have a font have sets of ligatures per <whatever you're working with right now>.

That said, however, the article fails to provide a compelling argument against ligatures.

1. Fonts have nothing to do with Unicode. It's exactly the font's job to provide any glyphs or ligatures it wants on top of provided characters.

2. Programming languages have been long stuck in ASCII-land trying to emulate symbols commonly used in other areas such as mathematics: -> and => are arrows, == and === are equality and congruence, >= and =< are greater than/less than or equal to, and the list goes on. These will never be easy to type in their original form (unless you have APL's custom keyboard), so why not present them as such?

3. Computers have all but destroyed typography, and it's a good thing some of it is coming back. Properly spaced numbers? Properly spaced and aligned punctuation? Contextually correct punctuation? Yes, please, more!

So, what's the beef with ligatures? I don't know :) And yes, I've been using Fira Code for several years now.

Ironically, the article says "well-intentioned amateur ligaturists are adding dozens of new & strange ligatures." and uses what appears a "° DEGREE SIGN U+00B0" that looks like a link to a footnote to denote external links.

Edit: minor corrections to readability