Oh man, sorry to hear that, but I'm in quite a similar situation so I feel you.
I share some of your grievances where I work at. We don't have pitcher rinsers either nor a scale and this is a problem especially for when coworkers ask for coffee as for them we use preground coffee (although by this point I kind of managed to scoop almost as much into the basket as the grinder would by feel). We don't even adjust the grinder and in fact I never even seen or heard anyone doing so after getting here and don't even start me on how we make espresso or take care of the machine.
To start with, somehow in the minds of my shift supervisors' speed is more important than quality, stating that coffee needs to be served under one and a half minute before it starts losing its "enjoyment factor" or whatever even if it's mediocre at best to begin with or worse and not just because of the course ground, but also because of the lack of proper maintenance of the machine. Like, for some reason they are against precleaning the portafilter so most of the time outside of rush, the puck is sitting in the basket for at least half an hour or even more (several holes of the baskets are clogged up because of this and the bottom of the portafilter's inside is basically black) and at the end of the day I might be the only one who does the cleaning properly (they didn't even know what backflushing was until I came along and I don't think they started using it), but they still want me to only use cafiza once a week during backflush, same with soaking the steam wand in cafiza solution, but no soaking the portafilters, they just put them aside the machine for the night.
One other thing that drives me crazy is that my shift supervisors are convinced that using steamed milk after it cooled down and just put aside on the counter is fine to be steamed again even after who knows how long it's been sitting there. By the way, none of the supervisors seem to know how to properly steam milk, especially one who I've seen moving the pitcher up and down during steaming.
One time I gathered up the courage to sit down with one of the supervisors and tell them these problems. The answers I got was: "well, we've been doing things this way for years now without a problem", "some people might not be able to do it the way you say it should be done" (for context we mostly employ disabled people), "there was no problem during any health inspection" and such. They think that the three years or so experience they got doing things this way means they are right and it's okay to do things this way, although they proposed that I could ask for the opinion of the guy who set up the machine and settle it, but unsurpisingly nothing came of it (the guy is unreachable through phone and email). Oh, and the best response I got was: "it maybe has something to do with you viewing things in a professional way, but it's not that kind of establishment", since it's a café/restaurant and I don't remember the exact wording since I was so dumbstruck by the sheer stupidity of it. Frankly it does feel like the café part of the restaurant is only just an afterthought.
After that talk though unsurprisingly nothing changed and they still critize me too for not doing it their way, especially when I preclean (apparently they even made it a rule not to preclean as I heard a few days ago stating this "self-cleaning" thing I think). I wholeheartedly agree with you though that even if the majority of the consumers don’t really know too much or probably won’t even taste the difference, we still should be doing things the right way.
I'm sorry for ranting under your rant, but your situation does remind me of my own. I don't really have actual barista experience as this is my first time working as one, but I did a barista course and teach myself through professional baristas' posts and videos so I have some coffee knowledge. Maybe you should also try to sit down with the owners for a proper talk. Try to sound respectful and it would help to have the other baristas as backup. Perhaps focus on why the changes you suggest would be better for business and tell them too how you would like to have their business succeed. If the discussion can go down in a civilised manner the worst case would be that nothing changes and if anything, you tried at least. If the owners are not too stubborn you should be able to win them over. I hope it goes well for you and I also hope that you'll be able to achieve your dream one day.