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!
They weren't as buggy. People making excuses classify exploits as bugs ignoring that modern games have more bugs and exploits.
I played Atari 2600 games like space invaders, adventure, and pitfall for thousands of hours without ever running into a bug. The only game with an exploit was Combat where you could put your tank muzzle into a corner and make it loop across the map. But both players could do it.