Ideally, good manners are all about thinking of others before yourself. If you’re fitting into that category, I would say you’re doing fine.
To illustrate, my mom has an older brother, Alvin (I mentioned him on another thread), who used to rock up to family Thanksgivings and Christmases at my mom’s house with his wife. My mom hosted every year. Alvin and his wife never hosted, never cooked, never helped, always arrived half an hour late so the food got cold, and left immediately after dessert complaining about the long drive home they had ahead of them (they lived 30 minutes away).
They would actually bring Tupperware containers with them, and I remember very clearly them hovering around the dishes as soon as Alvin had put his dessert fork down, filling up the containers with food my mom had bought and cooked. I remember them taking massive pieces of turkey (think entire drumsticks, etc.) and the most expensive food items, half the cake, filling up multiple large Tupperware while my mom watched awkwardly. A couple of times she had to step in and tell Alvin that we needed that for our lunches, or that she meant to send some turkey/pie/etc. home with their mother, our grandmother. It was so awkward.
After a year or two of this my mom wised up and started putting leftovers away before she served dessert. At leaving time she would offer a slice or two of one or two items and provide her own small container to put it in. Seemed to help. Ah, memories.