You know the solution to that problem as well and yes, it is to use more technology to filter out prompt injections. It is an arms race just like any other, comparable to the missile vendor who sells missiles to country A, anti-missile missiles to country B, anti-missile resistent missiles to country A, anti anti-missile-resistent-missile missiles to country B, etcetera.

It is a strange game, the only way to win is not to play. That is unfortunate since that'd mean the free software era has largely come to an end.