If anyone tries to describe it to you in terms that don't mention how silly it is, they're omitting a significant element that defines Cat's Eye as a story.
Cat's Eye, the group of art thieves, have a deus ex machina on speed dial for every predicament they find themselves in, and if you want a competent crime manga with a thrilling but realistic story, this isn't it. Cat's Eye always has something in their back pocket, even if it directly contradicts a panel showing you otherwise. Hojo kinda just didn't give a fuck while he was drawing this, and it's fun, because watching police get outsmarted by some hot girls that always know better is a treat in and of itself.
The romance is actually the best part here, managing to develop horrendously slowly and yet at a completely believable pace for the characters you're watching. Toshio, the MC, is delightfully pure of heart and mind and dedicated to his girlfriend Hitomi, who couldn't possibly be Cat's Eye, the thief, despite never being seen in the same room as Cat's Eye (thief) and also working at a cafe called Cat's Eye (yes, really). The manga's endgame that you're reading for is less "Will he catch Cat's Eye?!" or "How will Cat's Eye outsmart him this time?!" and more "HOW MUCH LONGER IS HE GOING TO MISS ALL THE RED FLAGS THAT HIS GIRLFRIEND IS CAT'S EYE?"
The thing is, the dei ex machinis and absurd elongation of a bonkers romance aren't a detractor so much as a selling point. Cat's Eye is juvenile, but sometimes, that's just what you want in a manga. It's not overly complex--despite how the talk of complicated burglaries and syndicates may make you think--and it's a fun read to see where the characters end up, as frustrating as they all may be.