EverNightX: If you can't make your own engine YOU DON'T KNOW HOW TO MAKE GAMES. You just know how to use Unity. Or you know how to use Unreal. But take those products away or the people who made them die off and they can't be maintained and guess what? You can't make games anymore. Because you don't know how.
We need people who know how.
The people who know how to make games are the game designers and writers, who come up with the gameplay and story and characters and what not. You can't do without those, and they need to work on each game specifically.
Then you have the artists, who flesh out the game's atmosphere, look and feel. This can be accomplished by common or purchased assets, but it can't possibly turn out anywhere near as well as when it's customized for the game. But even those custom assets can be purchased or done by contract workers, though they will need to be actually done for the game and those workers will always have an amount of creative freedom in them.
The programmers implement all that, and while you obviously can't have a game without them, their job is just to implement, to make the game do what the designers and artists want it to, so very much a job for contract workers with no actual say in the outcome. Which means they can also be indirect contract workers, as in those working to create the tools used by the designers and artists to put together their game.
Custom engines are good because they're tailored to the game, as opposed to trying to make a game according to the options offered by the engine, and because they can be optimized, while generic engines, even more so those made for multiple platforms, are utterly terrible in this aspect, hence the insane system requirements compared to what the games actually deliver for so many years now. But, while good, they're in no way necessary.
(Not so) random example: Bloodlines. It's a great and memorable game because of its design and artistic aspects, and despite the use of a 3rd party and, at the time, immature engine and being an awful buggy mess in terms of coding.
How many games can you say are great and memorable because they are competently coded from scratch and despite the awful design and art?
(PS: Unity sucks and shouldn't be used for many reasons, starting with the "telemetry", but this discussion went way beyond that.)
