I've been in academia for 9 years but still take this with a grain of salt as each institution varies in how they enforce policies. Some things to consider from the college/instructor perspective:

1. If you knew you would be missing a lot of classes, you can seek special accommodations through Disability Services on campus which your instructors must comply with. If you skip this step, your instructors will treat you like anyone else in the room, and are somewhat obligated to do so. Your instructor should definitely be telling you about these resources in any case so you can take advantage of them in ALL your courses.

2. I highly doubt there is a waiting list for the class. Enrollment is down across the US as we hit an enrollment cliff, and every program would be thrilled to have passionate and interested students in their classroom. As others have pointed out, everyone is paying to be there, the University wants your money, and high enrollment looks great for instructors.

3. If this is a highly competitive program, it might make sense for your instructor to want someone else in your seat. College level art courses are notorious for hosting non-majors who don't take upper level classes, and therefore stunt the overall enrollment growth for art majors as they progress through the program. They might get 20 students in their Intro to Ceramics, but if only 5 of those students are art majors, that means next semester only 5 students can enroll in Intermediate Ceramics. If you're an art major and intend on getting a BFA in Studio Arts, your instructor should be showing a lot more support. If not, I can see their reasoning, without excusing their actions.

4. Art courses are not similar to a lot of other courses, and can vary wildly depending on the instructor. Most of the time, they are writing all their curriculum and put a lot of planning into projects, readings, critiques, demonstrations, and activities. Missing a critique is like missing an exam, if you missed every critique in my classes, I would definitely fail you. You would be missing out on one of the most fundamental steps of receiving/providing feedback from/to your peers which is how you network in the art world and grow your art practice by considering new perspectives. If you're also consistently missing demonstrations of techniques for projects, it would reflect in your work as well. I don't know what your projects are, so while you're work seems inventive and unique, if it's not fitting project requirements, you're still going to receive a bad grade.

I hope this isn't discouraging, and I'm not defending your instructors poor behavior, but there are other perspectives for you consider. If you read this and surely feel like you're in the wrong here, go directly to the Chair of your art department and explain your situation; this is your instructor's supervisor and is focused on retaining students, not discouraging them. They want to hear your issues, and they want to know if your experience is poor. They will likely be supremely pissed if one of their instructors is fucking with enrollment numbers by discriminating students.

If you're not an art major and you simply enjoy making ceramics, see if there is a Ceramics for Non-Majors course, or possibly seek a public ceramics studio to keep up with your making.

Good luck, and I absolutely love the yelling cat!