I've no idea what your first language is, but your English is pretty good.
I'd argue that you've just seen a snapshot of what goes on throughout higher education. There will always be a proportion who just fail to engage with the professionalism of the subject they're trying to study.
When I was an undergraduate I can remember a few in the University Air Squadron who didn't take it seriously enough - and they didn't last.
When I was teaching on a university flight programme, we had a few who didn't engage properly - not turning up for flying, inappropriate clothing, one even who was clearly spending rather too much time stoned. Similarly on the engineering part of the programme, those who just studied to pass the exams (if that), and weren't really trying to become proficient in the subject.
Those of us / you who engage properly and try hard to act like professionals, usually will end up as professionals.
Those who don't, will either learn, or will end up working in non-aviation non-jobs.
Frankly, there's little value in worrying about them, as mostly they're only wasting their own time and money. Learn your version of professionalism from the people paid and qualified to train and educate you - and don't get dragged down by people who don't grasp it.
That said, you are students and you're not in front of fair paying passengers. A uniform alone certainly doesn't create a professional - and try and see past their informal dress codes to the real level of professionalism they're displaying.
You might just discover that one or two look unprofessional but are actually really professional in their behaviours, and vice-versa. Epaullettes matter much less than correct cockpit checks.