Would it get someone to a B1 ability or more a2?
Personally (!), I don’t think the Memrise courses alone (!) won’t get you anywhere near A2 by themselves. They’re really only a bunch of vocab (no, I’m not downplaying them at all!), garnished with a few sentences here and there.
That said, you would have to add grammar and maybe something like a more sentence based approach and, possibly, a language class, instructor or something alike. That is, unless you’re living in a country where your target language is being spoken which is of course the most reliable and quick means to learn a foreign language.
My personal approach is to use both Duolingo and Memrise which I do think can get you to A2 or even B1 (depending on the language and courses offered). I usually work through the official Memrise courses first, then I pick community courses, particularly slang courses and those 5k monsters.
Then it’s on to reading books (bilingual first, then target language only) and watching TV/movies/videos. Of course, talking to people in the target language helps a whole lot. As a German this is, for many languages, somewhat easy as there is so many people speaking foreign languages here (for instance, Turkish, Italian and Spanish is all around me here) and I can easily (pre COVID anyway) hop over to i. e. France or the Netherlands and talk to people there.
But then again, that’s only my 2 cents.
Another tip is to listen to their local TV or Radio (over the internet).
Children’s stories or well spoken items like the news, when you know what’s current, helps.
I have recently downloaded “Radio Garden” a map based app to tune quickly to any country or town and often be presented with multiple radio stations.