Here’s my take.
If you make a new modern headliner, if it’s fantastic today, it’ll be at least great 20 years from now (see Disneyland’s Indy).
If you make a mediocre filler ride, if it’s good at opening, it’ll be bad 20 years from now (see WDW’s Buzz).
In terms of filling out a park for quality and capacity, if you build new E-tickets/headliners, you’re resetting the goal post. The old top rides drop down a peg, the next top rides drop down a peg and so on and so forth.
E-tickets generally have higher capacities than Cs and Ds due to their larger scale.
And I know people will cry foul “but Es make people want to come! So it’ll counter any capacity net.”
And like, okay… I’m a parks fan… I want to do things I want to do. I want to do things that are good, not simply filling my time.
I have nothing against flats or Cs or Ds they match the execution and vision of the ride experience, but the cries for almost exclusively mid-tier experiences are silly.
The price per capacity added for a C or D ticket is not that far off from an E. The barrier of entry for creating a project of any scale is very high, that if you’re going to make a project, you might as well make it good, or save until you can actually afford to make it good.