GPTs not much better than using GPT directly?

Instructions are indeed constantly modified when you interact with the builder. However, the builder chat is well suited to explain how to better go about eliciting the behavior you want while staying within the 8000 character limit (and at troubleshooting other issues). To counteract it, you can tell the builder you are only fleshing something out and do not want any instruction adjustments made without express permission. When you give permission, ensure you tell it to only add the new instructions to the end of your current ones and not to modify anything. This method is not full proof, but it does give you the chance to go back and fit your instructions in how and where you deem appropriate.

So, this may seem like a 101 level statement, but it seemed like the best time to point it out:

Remember to always save your ‘instructions’ progress in an external document where you can keep track of changes and iterations. Losing 8000 characters of well thought out prompting because the builder misinterpreted something is beyond frustrating.