If you put yourself in the position of this not being a summer job, but a real job, then it would likely not be a career either. It would be a stepping stone to working on areas with more responsibility, allowing you to pick up expertise with the full operation of the production line. You would have to have zero ambition to do it for your entire life, and I've not seen many people who did; there's always progression and more responsibility even for those who don't have a good education, but do have a desire to improve themselves and show they are capable.
I used to work in a brewery, as an analytical chemist, but this also involved some time on the bottling and canning lines taking samples and calibrating the equipment, so I did see a lot of what went on, from the depalletisers loading the empty cans and bottles onto the conveyors, to the fillers, pasteurisers, labellers and the packaging and warehousing. They did employ a number of temporary workers to do some of the simpler stuff, like what you were doing. But since each line was several million pounds worth of state of the art German engineering, the people operating and maintaining it were well compensated for their expertise. If you'd stayed, then you could have worked your way up the ladder to do that, perhaps including part time study for an engineering degree or industry-specific qualifications.
A lot of industries like this do have good prospects for career progression. But they do require time to be served at the bottom before working up the ladder. And even the bosses have to do the menial stuff when required from time to time; I've seen the production site manager doing your job when they were caught short-handed. One of the great things about this environment is that you have everyone working across a whole site in synchrony to make the whole process work; and on the site I worked at, it was a great place to work.
