Although I’m a firm supporter of free software

Unless I'm misreading this, your argument seems to be that software freedom is irrelevant in the face of technical superiority or popularity. That's exactly the opposite of "firm support" in my view.

I'll offer a counterpoint to the "best tool for the job" thing: before git existed, Linux development relied on a proprietary VCS called Bitkeeper. Licenses for Bitkeeper were "graciously" donated for gratis by the Bitkeeper developer. Andrew Tridgell, who was not party to the Bitkeeper EULA, telneted to a Bitkeeper server and typed "help". The Bitkeeper developer, in retaliation, revoked the Linux developers' gratis license to use the proprietary "best tool for the job." This was what forced Linus to develop git, which became the most widely used VCS in the free software world. (read: Thank You, Larry McVoy by Richard Stallman)

Proprietary tools can seem to be useful in the moment but developing a dependency on them, and encouraging their use, is dangerous. Discord might seem like "the best tool for the job" until it enshittifies, just like its predecessors did, and just like its successors inevitably will. We've seen it happen often enough.