I can understand where the article is coming from, she's similar to Whitney as in she's the "Voice of our generation" and she primarily sings power ballads that go on to become mega sellers that will all end up becoming classics.
But artistically, they're very different. Vocally, Whitney Houston in her prime was the best vocalist the music industry has EVER witnessed. Not even Adele can touch Whitney when it comes to vocals. That's not to say Adele isn't a fantastic vocalist either, because she is. She isn't as technically skilled as Whitney was, but she's still more technically skilled than any other vocalist from this generation (Beyoncé does not count as she is not from this generation) and the thing about Adele is she is very emotive. She has that over Whitney. And again, Whitney was emotive in her songs as well but Adele is the master of emotional vocals.
Artistically, Adele shines because she writes everything she sings. We get a sense of who Adele is as a person because her music is very personal and introspective. Whitney didn't really have much artistic identity because she was pretty much just handed songs on a silver platter from Clive Davis and David Foster. But, if anyone deserved to have mega smash power ballads just given to them, it was her, so I'm not complaining. NOBODY could sing songs like "I Have Nothing", "I Will Always Love You", "Saving All My Love for You", "Greatest Love of All" amongst others like Whitney could. It's so cringeworthy when her songs are over-sung by people who audition on X Factor, the Voice, American Idol, etc. because nobody will EVER sing a Whitney Houston song better than Whitney. No one.
Truth be told, both women are fantastic artists and are the embodiment of raw, God-given talent. Whitney Houston is a music legend, may she rest in peace.

Adele is already on her way to legendary status and will most DEFINITELY be the most remembered, respected, and impactful artist of this decade. She outshines her peers effortlessly on so many levels. Just compare her to any other mainstream act that has debuted this decade (with the exception of literally only Bruno Mars who she wrote the flawless future 6x platinum #1 'All I Ask' with) and you'll see what I mean. She really is in a league of her own, just like Whitney Houston was.