I made this mistake when I began. I wanted to learn contemporary rock and I did it by studying with classical singers. I learned a lot about classical! Luckily I enjoy opera and love to sing opera. But did it improve my rock voice? Not really.
In fact, operatic technique is notoriously rigid. You stand a certain way, breathe a certain way, and position your tongue, jaw, larynx in an absolute way. It’s based off of pre-scientific tradition so generally the techniques are steeped in myth.
Sure, the basics about singing are true. But how those basics are translated vary widely within the styles. For example, country singer’s use less lung volume than classical singers. The breathing technique you would be taught in classical won’t necessarily apply to country. So yes, you need to breathe to sing… but how you breathe is significant.
If you sing classical, then you can sing classical. I don’t have much else to say about this. Someone who plays finger-style classical guitar can’t just pick up an electric and begin sweep picking just because they know “classical technique.” There’s nothing special or technically advanced about classical styles; they’re just older.