These are useful under few circumstances only.

Faith projects improve all holy sites, this with Angkor Wat is worthwhile to spend production on. Rare circumstance that you need a few xp points so your units come with one or 2 stars of xp, then it makes sense to run a project to increase XP. This is very rare as it's usually always better to just create more units. Lastly, end game when everything is done and it's rare to get this part. Then using all projects especially gold and food if all tiles are in use. 

Can I propose for projects to improve the infrastructure should like the faith does. 

The stability project should instead improve all forts or commons stability. The food project should improve farmers quarters and so forth. 

Creating a district is always better than running a project. They are underwhelming and could be turned to something that players can actually consider if they provide something better.