.. Isn't this how doom was more or less sold? It was a one of the classic ID software shareware games, where you'd get part 1 for free and then have to mail order further parts.
Not really. Modern games will claim to be free to play, with many parts of the game hidden behind microtransactions, or they'll be paid with the option to buy more.
Doom never claimed to be free to play. It was always 100% up front that the shareware version wasn't much more than a playable demo. The paid version of Doom was the complete game.
