If WOTC makes something new, I am sure they will look and make that choice again.
Speaking as a 3.5 fan, I completely agree. All WotC needs to do is produce a better version of D&D's original 1974-2008 gameplay and I'll be all over it.
I'd like to know why Essentials did not do as well as I expected, what piece of evidence I missed.
If I had to venture a guess, I'd point to three factors:
(1) The pay-to-preview Starter Set isn't an effective product. (Products like it have been tried more than a dozen times by TSR and WotC. They have never been big sellers.)
(2) The total price point for the softcover Essentials books is higher than the hardcover PHB/DMG/MM trio. So any new players doing price comparisons will figure that they're getting a better deal by PHB/DMG/MM set.
(3) WotC was probably a little too hyper-interested in avoiding another "3.5". They invested a lot of energy into convincing anyone who would listen that Essentials was 100% compatible with 4E and that absolutely nothing was changing. It's really hard to convince existing players to buy something when you're telling them that they already own it.
(4) The Essentials rulebooks didn't actually fix any of the problems that the vast majority of 3.5/PF holdouts had with the 4E ruleset. (Someone like that probably does exist, but honestly the only people I have ever heard claim that Essentials would appeal to 3.5 players are existing 4E players.)
So you've got a product line that doesn't sell to new roleplayers; doesn't sell to existing 4E players; and doesn't bring ex-customers back into the fold.
That's a product line with some problems.
Also, check this out:
(1) Go to wizards.com. Click on "Dungeons & Dragons". Click "New to D&D". You'll end up on this page, which features two videos telling you to buy the PHB/DMG/MM.
(2) Do a Google search for "what do I need to play D&D". You end up on this page on Wizard's website which also tells you to buy the PHB/DMG/MM... for 3rd Edition.
There are, obviously, pages out there telling you to buy Essentials. But there's some dysfunction here in WotC's message.
More generally, I think WotC is really fighting the fact that they literally do not have any effective branding which translates to, "These are the books you need to buy to start playing D&D."
Core? They spent 2008-2010 degrading that term into meaning nothing at all.
Essentials? Even if you actually needed all 11 products in the Essentials line to start playing (and you don't), the idea that you would need to buy 11 products in order to start playing the game would be completely absurd.
The Starter Set might have fit that bill, but they made it using a proven-to-fail product model.