But a possible way to defeat it is what I do now --- keep two devices. One that meets their requirements for cases where it is absolutely needed and another for everything else.
Of course it's dubious if it applies here, especially because the playing field doesn't feel quite equal, but I think the most effective thing we can do is simply refuse to use websites that require a custom built user agent to access.
Heck maybe we've already mostly lost the battle to keep the internet usable with curl, let's at least try to keep some of the other options open.