I had the exact same thought. Pretty low probability that there's going to be a script-kiddie exploit for your custom tools. Pretty decent probability that there will be vulnerabilities present if someone cares enough to target you.
See e.g the lock screen gap that another commenter noted in a nearby thread.
Although everyone might use their own flavor of "database" or "REST API", I can't imagine every layout to be unique enough to not have similar exploit classes entirely. AI isn't known for being super original after all...