I don't even know how to approach such a question, but let me try.
First, budgets were different. The amount of people working on a game were different, and time schedules were different. So I've already established the apples vs. oranges scenario going on here. Secondly, anything a developer designs is a given input. Said input, requires "X" amount of resources. In todays games, the pricing and profit margrins are mostly the same, yet the amount of input has exponentially increased. HD games, higher audio/visual demands from the consumers, escalation of gameplay experiences etc. Because more input is required, additional money and development team is becoming more and more sparse, thus - you have less opportunity and resources to implement "additional/secret characters and modes" in a particular game. You certainly can, but that would require an increase in "input" - that can apparently only be recouped via DLC costs.
I'm not saying I like this - because I agree: Instead of making it a Free DLC via gamestop pre-order, they should instead of made it an incentive for new game purchases. That way people who don't want to or can't shop at gamestop or EB games have access to this DLC for free like others. But I'm sure, GAF would have still complained - citing that Capcom is violating their god given right to buy used games for having free DLC as a bonus for purchasing new. If I was Capcom I'd just not have made this additional Vergil content to begin with. The main game is going to be the main game, whether or not one knows about this DLC's existence either way. Would you rather have a completely new designed Vergil campaign...sure, most people would say yes. Should you take advantage of the fact that you can this DLC for free by pre-ordering, sure - if you like what you play when the demo comes out. But judging by the reactions here, Capcom should just hit the delete button on this extra campaign. Silly for them to think like that, considering the main game is what it is, and you have the option to not pre-order or not get the DLC.