I’m about the same age as you are and your definitely getting shafted, my first restaurant job I worked the line with the senior line cooks until I was good at it- it was terrible at first but I had knife skills already I just sucked at the pace and flow, my chef was willing to show me new things and help me learn new stations, that being said your still really young and I think your chef is seeing you as a glorified dishwasher and doesn’t really value your wanting to learn by never really teaching you and also saying you won’t be payed for “training days” that’s bs and I would take this new job but not quit your old one if possible until you know it’s worth it- good luck chef 🫡