I believe it. It does use too much software, and also too many layers of software.
However, it is not only that; too many other things (not only software programs, but also things such as 2FA, databases, cookies, Unicode, HTML, JSON, etc) are used in cases where they do not need to be used, or where something else would do better instead.
They mention React. I think GitHub uses React, although I wrote my own scripts to use instead and it is much shorter than theirs.