Yeah it’s some combination of
- The humans are racist
- The Gungans purposefully hide their level of tech from the humans
- It’s not just humans. Neimodians make the exact same remarks about Gungans being primitive.
- Makes sense. I would assume that prior to the events of TPM, any Gungan who travelled outside of the city would feign having little knowledge of technology, until the Battle of Naboo forced them to reveal they aren’t primitive at all.