English Translation
John and Cathy have different tastes and different characters. Trying to get them together is like putting a square peg in a round hole.
興味 is an incorrect translation for “tastes”. It should be 好み（このみ）or 嗜好（しこう）.
興味 means “areas of your interests” – e.g. I am interested in music, but not so much in watching sports games.
好み or 嗜好 means “taste” or “preference” – e.g. You and I are both interested in music (= sharing the same 興味). But you like rock music and I’m a big fan of classic music. So, we have totally different 好み in music.