so maybe this is normal, but I’ve had the same story going on for over a year now, and it’s really starting to burn me out.
Get used, it's normal in some cases - projects that are most likely failing and will never deliver anything productive.
Think about this way, that . While they're postponing you're making a couple of improvements you're getting payed for something that is now very in your comfort zone and you've to do a little to no effort to deliver some progress.
This is a management issue, may have come from poor requirements, high expectations, ineptitude in software dev. project management or all of the above combined.
Your best course of action is to realize that it's not worth for you to burn yourself trying to deliver more than expected or jump ship. Just do whatever you've to do at the pace you feel comfortable, wait for the project to fail and move on. Jumping ship won't help you much, it will essentially degrade your professional image and force you to learn an entire new architecture of another project that may end up just like that one. :)