Thankful does not mean content.
Imagine you are lost in the desert with only a few drops of water to keep you alive. After 4 days, a search party finds you leaning against a saguro cactus barely conscious. They give you a astronaut style dehydrated snack to give you enough energy to make it back. In this critical state, you are immensely thankful for the nutrients and your severe hunger masks the bland taste.
Does this mean that you are content to eat dehydrated astronaut food for the rest of your life? Will you never want or need to have a crisp apple, juicy steak, or glass of wine?
Of course not and nobody would call you insatiable or greedy for feeling that way. Being thankful for what you currently have is not a life sentence to remaining with what you have. Wanting something else is a sign of growth, not arrogance or greed. Don’t use modesty and humility as an excuse for expanding your boundaries. Be thankful for what you have and unashamed to reach beyond.