So, that's NOT the sunk cost fallacy. If you are still getting benefit from the cost, it's not sunk*. This is just not wanting to invest time into a new system while you're still productive in the current system. A sunk cost would be like, "Well, I spent $100 on this steak, so I'm going to finish it, even though the next bite may make me vomit." In that case, you paid for the steak, it cannot be returned half eaten,…
So you end up lying to the floor with parts strewn around you more often than you'd like to. And what you really want to do is go places in your car (ha...ha....ha) than be a mechanic.
I've programmed Go using Emacs for 4-5 years (and I've used Emacs for 30+ years). To be frank: my old Alfa Romeo from the 1980s breaks down far less often than the Go tooling in Emacs. Or the Java tooling before it for that matter.
It's not that I no longer like Emacs. It is just that I like programming more than I like doing redneck-repairs of Emacs.