It’s always more work than it looks. You can get to mostly usable tools quickly if your request isn’t too difficult, but every time I use them I run into another thing that needs to be fixed, changed, clarified, or cleaned up.
It’s fun at first, but over time you realize you’re spending more time building the tools than using the tools to build the thing you originally wanted to work on.
I think personal software is best for highly specific tools or for things you need to use repeatedly for a very long time.
For something like a SketchUp competitor, I wouldn’t want to try to maintain my own. The number of edge cases and features is bigger than you imagine up front, and the vibecoded version that might appear a few hours after your prompt is going to be very far from the version you want to use.