Ignoring the lack of updates if the game is buggy, games back then were also more focused on quality and make gamers replay the game with unlockable features based on skills, not money. I can't count the number of times I played Metal Gear Solid games over and over to unlock new features playing the hardest difficulty and with handicap features, and also to find Easter eggs. Speaking of Easter eggs, you'd lose a number of hours exploring every nook and cranny finding them!
I don't see how the amount of "completeness" can even be measured. Is it really so much worse that you can buy extra fighters for the Street Fighter 6 that you already own rather than buying Super, Turbo, and then Super Turbo at full price every time? Or that you can choose to buy just the stuff you want for Cities: Skylines for half the price instead of paying twice as much to get stuff that don't care about along with it? Plus, expansions like Phantom Liberty and Shadow of the Erdtree are bigger than most entire video games from the 90s.