Clearly as an aspiring Mustachian you've seen the error of your ways, which is great!
From my perspective, borrowing money to buy an expensive car is just about the most insane thing one can do - the car plummets in value, while you pay a lot more than what it was originally worth because of interest. Madness! This (along with credit cards) gets so many young people (men especially) up financial sh*t creek without a paddle.
Admittedly I'm far from perfect. When I was younger I went through a phase of buying near-new cars (thankfully I wasn't mad enough to buy something brand new). But I never took out a car loan. Later I calculated that I'd thrown about $20,000 down the toilet in depreciation alone. After that revelation I bought a ten-year-old Honda Civic for $5K cash, which faithfully served me for about ten years with barely a niggle until I sold it for $2,500 (after inheriting my parents' slightly newer Honda Fit - a move I later regretted, but that's another story).
From a financial viewpoint, cars are nothing but a necessary evil. (Those who see a car as a status symbol which makes them feel superior may want to take an in-depth look at their attachments and insecurities.) A car is a money-sucking metal box on wheels to get you from A to B a bit quicker (when you're not stuck in traffic), that's it. So IMHO one should buy the cheapest but most reliable (Toyota, Honda, or Hyundai) vehicle one can find and keep it well maintained and hang on to it for as long as possible.
Or keep it until EVs are no longer bleeding edge, and a long-range EV can be bought reasonably cheaply second-hand. Fossil cars are rapidly being obsoleted by EVs (some EVs are far quicker than just about any petrol car on the road, but you probably know that). So the depreciation on a fossil will likely be massive when the tipping point comes, probably sometime in the next 5 years.
So to conclude this long rant, I'd agree with other posters that you should consider selling the GTI before it depreciates further, and get rid of that car loan before flushing too much more money in interest. I don't know how much cash that would leave you with, but you could probably get a reliable used Japanese or Korean (definitely not European) car for less than $5K. I'd suggest NEVER borrowing money to buy a car ever again if you can avoid it.
Leasing seems a waste of money to me too, though I have no experience with this.
I've been mocked sometimes for my old Hondas - mostly by people who are still working their asses off to support the car loan on their brand new money pit. Having retired at 35, I don't care.