In the case of something like Stitch's Great Escape or Fast & Furious: Supercharged, yeah get rid of them. But you need attractions like TSI, Country Bears, all of the Fantasyland dark rides in Disneyland, all the small experiences at Efteling or Europa park to build out your capacity. No, people won't flock to them, but there's still many people who find a lot of enjoyment there.
Building only e-tickets is bad business, because while you get that initial bump in attendance, you're still offering a miserable experience if you don't build out your capacity and it builds disinterest among your consumers, which is what I think Disney is actually currently experiencing with its massive attendance drop.
I don't agree at all. Pretty much every park but Magic Kingdom desperately needs C and D tickets. Also, TSI always seems to have a consistent flow of people. It's a quiet respite from the crowds of the park, which I personally find valuable and I'm sure many others do too. Magic Kingdom has huge areas for expansion if they chose to use it. They have buildings sitting empty or otherwise builds "big" expansions like New Fantasyland or Tron which really waste a lot of space instead of compacting things in. They can build capacity but refuse to do so and replacing less popular attractions that many still enjoy only builds resentment.
It's a well designed explorable area that is appealing to kids and a relaxing place for adults. I've never seen anyone appear bored on the island. Like the Swiss Family Treehouse, it's capacity that many people will enjoy but never rave about, yet is still very important to the balance of the park.