If DLC didn't exist, games wouldn't have the production values they do now. Games can cost tens of millions of dollars. That is $10,000,000+. Reports lead to game budgets of AAA title releases within recent years hovering around the 60 million range. When you're working with budgets that large, time most certainly is money. So often times, games will ship earlier than they should to achieve a release date that investors are happy with. Games that may not be planned with DLC may later down the road release content they were already working on, but had to cut due to time and budget constraints. That way, the people writing the cheques don't have to lose more money while that content is made before release, and they get their investment back when that content finally releases since it costs money. That's not to say you're being charged for content you were supposed to get for free; you're being charged for content you wouldn't have received at all because of time constraints, and if they give it to you post-release with a price tag on it, they get to keep the higher-ups happy while being able to finish what they started.
Not to mention that when you invest a certain amount of time into making a game, you'd like people to keep playing it for quite some time after release. DLC is a great way to get people to either keep playing, or come back if they had stopped. DLC usually funds the support games get after release, anyway; patches, bug fixes, balance changes, etc. all happen because DLC can fund the devs' continued work on the same project. Without that DLC, they'd have to immediately move on to the next project, as continued support wouldn't be sustainable if there's no money to pay them for the additional work. That's why often times, after the final DLC is in the market, support for a game will end shortly after. There's no more income, so there's no more development that can be budgeted.
So, to answer the question, what would games look like without DLC and patches? Games would take longer to come out, not have the same production values, probably not have as much content, DEFINITELY wouldn't look as good as they do, and probably wouldn't be able to advertise the game. Games potentially would be more stable and bug-free on release, but if an unforeseeable oversight DID become a problem, it wouldn't ever get fixed, since you need prolonged sales and DLC to fund those fixes.