It's the same for wonders if, for example, you mistakenly start it off in a low production city next to your high production one.
I raised a bug report on this with 2K. I said players should be able to repurpose district and wonder tiles, at least during their construction phase. Not to allow that is unnecessarily punitive on the player for what's usually an honest mistake (only fixable by loading a save), and it's completely unrealistic as a parallel of real life.
The 2K guy was sympathetic and indeed shocked that it was like it was. However, in conversations with the developers, he found out that it was deliberately like that. I was appalled. There should be some way to repurpose it, even if builders have to be involved taking it apart.
By the way, I found a way round it - for wonders at least - without loading a save. It's pretty crazy and it can't be guaranteed to work because it relies on the proximity of the tile to the edge of your empire and it needs an aggressive neighbor. It's also very disruptive and takes a lot of time. What one can do is this:
- Provoke a neighboring civ into declaring war on you.
- Withdraw all military units from the city with the aborted wonder.
- Encourage the other civ to attack and take that city. When it becomes theirs, the incomplete wonder build will disappear and the tile will become cleared.
- Counterattack immediately and retake the city.
- Negotiate peace. You can now repurpose the tile.
I haven't tried this for districts, and in any case you shouldn't have to do this!
The district system is wonderful. I want to keep it. However, THIS HAS GOT TO CHANGE.