Here's my 2 cents: Suck it up and finish the degree. 

On a much lighter note, I fully understand where you are coming from. Architecture definitely requires passion to continue in but at this point you won't be doing yourself any favors by quitting early and switching. Does you school have an animation degree? Are the requirements similar? Switching may accrue additional classes and push back your graduation for no reason. What type of animation are you interested in? 

as opposed to someone that is in a totally unrelated field you actually have the advantage here. Treat your architecture degree as a design degree only (which most are anyways). Do you best in your classes and design work as pure design and less about architecture if that helps. In this day and age you can actually use your animation skills in your architecture work and make that a part of your motive. 

In any free time you have (and yes I know arch students don't think they have free time bc I never did, but after working full time I realize I actually had a lot more than I thought I did) learn animation skills online and practice a lot. You could also take an elective course in animation if it is offered. It may even be possible to get a minor at this point if they have one. My school tuition was based on segments of class hours so it cost the same for 12 hours of classes as 17 hours of classes. So if there's something you want more formal teaching in this may be an opportunity to add extra hours.

Finish the degree and decide later. I don't know the details of animation jobs but if you are pretty good at adapting and figuring things out i don't see why you couldn't swing a job in animation with an architecture degree. A girl in my class graduated and went to work as a sketch artist for high fashion brands in fashion weeks and editorials... keep your options open but finish the degree

Counterpoint: switch to a degree that will pay well if the whole point is you need a good "backup".  Imagine finishing an undergrad in arch, trying your hand at some animation jobs and that going nowhere, and then 3-4 years later, walking hat in hand to arch firms to accept a low-paying intern job.  In reality, unless you have no work ethic or skills, you'll get paid the same amount sticking with some sort of mediocre animation career, and if you don't have a work ethic, your plan 'b' architecture career won't fair well either.

Architects deal in light and shadow, texture and color, massing and proportion all of which are related to animation. I would finish the architecture degree and then make a determination. Enjoy and look forward to the artistic part of your remaining three semesters and just plow through and complete the technical part without complaint. Three semesters is a flash in time. 

Always finish what you started. 

I would finish the degree doing the minimum work on the technical side and focusing on the artistic side.

A lot of people who graduated with me went into somewhat related fields after school. Some went to architecture proper, some went to city planning, some went to graphic design, while others went into real estate investment business. Some left the field completely. One guy became an illustrator for magazines and newspapers. One guy went into retail.

Architecture is a very broad field that allows you to focus on one thing that you like about it. There is a lot of architecture-related work in animation. Staging and rigging are perhaps the most closely related.

While the field of animation is a little crowded with graduates who have specific degrees and knowledge, I think that an architecture graduate would have good chances if they have a passable animation portfolio.

You can even do your final project on the relationship between architecture and animation.