Even so, it's the most recognized way to pronounce the name in English. Yahweh is also acceptable, but isn't as widely used.
The funny thing about it is that we also don't know how Jesus' name would have been pronounced for the same reasons, but nobody ever has an issue using "Jesus", but people say "Jehovah" and it causes a stir. ¯\(º_o)/¯
Well Jehovah's witnesses think it's important to use the personal name of their god, so it's a bit amusing that they get the name wrong. It's like they fell at the first hurdle.
To be fair, the mistranslation predates them. I see they acknowledge the issue and think it doesn't matter.
I guess it's a bit of a coordination/communication issue with other JWs and with the world at large. The fact that they stick with this mistake doesn't mean that individual Witnesses, or the group as a whole, are stupid, or don't understand their own religion.
The funny thing about it is that we also don't know how Jesus' name would have been pronounced for the same reasons, but nobody ever has an issue using "Jesus", but people say "Jehovah" and it causes a stir. ¯\(º_o)/¯