They can clone successfully, they can speed up the process with growth acceleration....still sounds like advanced tech to me.

Also, this is a fictional universe. I have no problem believing that things there are not necessarily as they are here. Perhaps, even with all the other scientific advancements they HAVE managed, cloning still eluded them until just recently (in their time) (a long time ago, in our time).

Not to mention that cloning (in SW) clearly ISN"T a widely held skill set, seeing as the Kaminoans are the only race shown who can actually do it.......so that particular in-universe reality is already dictated to us. If anything, showing the Gungans as also knowing how to clone, makes it more common....which actually DOES lend itself to the idea that it goes hand in hand with a more technologically advanced universe. Not everyone is going to be great at it, so they've left it up to the species who have particularly high aptitudes in that domain.

Also.....it's just a movie.