Nobody is lying to you or misleading you. Please read Javier's explanation a few posts up.
Teaching a bad habit would mean that they are teaching you something that is actually poor language use.
Example: Yo estás cansada. That's bad language use because it's grammatically incorrect.
Again, it's not bad Spanish use, it's a correct and acceptable form of Spanish. Even in the worst case scenario of you completely internalizing the use of vosotros (lol, the tragedy) , native Spanish speakers will understand you and not miss your point even if they don't use this form. If a native Spanish speaker from Spain goes to Guatemala, they will know immediately that they're speaking to a Spanish speaker from Spain. Nobody, literally nobody, will think it's bad language use. In your case, they will think you learned Spanish from Spain but nobody will think it's bad language use, lol. This seems to be a radical concept to some of you out there.
I have a group of people using this app to learn Spanish with me, we are all aware of the distinctions and it's not a problem, ever. And we are all focusing on Mexican Spanish, fully aware that they don't use vosotros in Mexico. Part of language mastery means you can tell these things apart and have no problem with them.
I'm learning my 5th language and I promise you that I'm always aware of the region-specific variants even if I don't use them without actually whining about it like it's the worst thing in the world.
The things you complain about aren't a secret in Spanish, it's something we learn almost immediately after learning the alphabet. Lingvist isn't misleading you or lying to you.
The reason why I asked this question here in the first place is is because I find this indignation so weird, some of you are acting like the Spaniard overlords are out to get you by messing up your life with vosotros and the reasons I have read are slightly more or less ridiculous than what you wrote.
Have a nice evening. I'm done here.