Earlier quoted context omitted.
It's not a sealed draft at all. You can purchase as many decks as you like, and you can also purchase from secondhand markets.
The most popular formats of Magic by far are "kitchen table" (totally casual, play with whatever cards you own), and Commander, a casual multiplayer format where super-powerful decks are generally frowned upon. Competitive Magic is a tiny tiny fraction of the overall market. It's also totally possible and reasonable to build competitive decks on Arena with a pure F2P account, if you're into that.
Casual Commander remains my all time favourite game. I miss playing it so much!