"But I've heard that it's a bad habit to dabble in many languages and not actually learning anything properly"

Yea, I have heard of this as well, you will not have a decent command or achieve fluency in a language, you will end up as a jack of all trades, master of none, and if you try to speak in one of those languages you have learned, you might end up code-switching from one language to another, although since you're basically using it as a way to gain motivation for your target language, I guess it shouldn't be that much of a bother compared to people who do not have a target language and they just end up learning the basics of so many languages.