It's not a question of "who's right" - it's a question of whose wedding and whose day this actually is. Yes, your parents live in their own logic where the scale of the event = respect for the family. But at the same time, it's your choice how you want to start your life together. If you're both into minimalism - that's already a strong position, not just one person's whim.
The main thing to think about: conflict over planning the event can ruin the day itself. If you fight your way through their resistance, the celebration might end up awkward, with hurt feelings and comments. Sometimes it makes sense to find a compromise not in scale (you don't have to choose between 30 and 150 guests), but in format - like, a modest celebration, but with touches that'll put your parents' minds at ease: a good photographer, videography, a beautifully decorated venue. It's not a massive party, but it looks "respectable" in the family photo album.
But if you really do want exactly the wedding you envision - that's your right. Just accept that your parents might be upset for a while. That's normal, it doesn't mean you did something wrong. Sometimes you just have to accept that family members are disappointed, but you still have to live your own life 😊