I kinda got bored halfway through. From what I gather they're salty that GitHub is switching to react? If that's the issue then the headline is rather misleading isn't it?
Surely legacy software is one that drifts into obscurity through lack of investment which is the polar opposite of GitHub rewriting their entire front end..
It's not an incidental detail when the text is almost entirely around the issue caused by this (mis-)use of react. The author doesn't give another argument to support their view.
There seems to be a rando paragraph about AI as well,then it trails off that they're looking for recommendations for git blame clients. I couldn't really figure out how it was all GitHub's fault or where the word legacy fits in.
The thing is a new feature - AI-related in this case - contradicts the idea of legacy software to me, so I really don't know what was the point of that other than "complaining about github".
There's a difference between the author being mad that github is switching to react and the author being mad that github is misusing react. It is possible to use react without breaking browsers find in page functionality, which is ultimately what the author is frustrated about.
Crappy old websites that don't behave properly with my browsers search function sound like legacy though. I agree the headline is worded a little strangely but I can see their point.