The creators of the OGL have been pretty open that people creating their own games as well as supplements was what they expected, and they deliberately made it so that if WotC did flake then somebody would create something compatible.
WotC flaked, and somebody did create something compatible.
I do not call a license doing exactly what it was designed to do a failure - I call the WotC folks that ignored the intent of the license, well, a lot of very bad things indeed.
The failure was not in the license, it was in WotC believing that D&D the brand had enough swing to succeed regardless of dropping that license. (And ignoring their playtesters, and in alienating a fair number of potential customers, and....) Hubris, more than anything else.
Well, if you're looking at things from the perspective of a long-time player only and only concerned about the game system as something that gets support from any old place, sure.
If you're looking at it from a business perspective, with the intention of ensuring the long term liquidity and business success of the company that currently owns the D&D license it's a different matter.
When you work for a company and you're responsible for a product line, yes, you're responsible for a product line. It's not your child and you're not responsible for it's long term growth when it's owned by some other company. You're responsible for ensuring it's growth and the success of the firm that's paying you and allowing you to put food on your table.
So while the designers of the OGL said "Hey the point was to ensure that the game lived on, even if WoTC flaked", just admitting that is saying "Hey screw the company I'm working with, the product is more important. That's an artist's view, not a business person's view and is ethically off if you're being paid by the company and not an independent artist.
Are the people responsible for the OGL still working at WoTC? I'd guess not.
There are plenty of examples of licensing that allow for the growth of IP in an open way, without giving away the farm and allowing a competitor to take over a core competency. Being harsh and admittedly this is my personal opinion based on limited information known:
1. Paizo's management looks brilliant.
2. WoTC's management of this specific issue was horrible and was either caused by high level negligence worthy of damages or replacement of legal counsel.
Meh, nuff said on this matter. I'm really enjoying a Pathfinder campaign right now and while I am running a 4e campaign at present, It's on hold. Major issue with announcing a fifth edition is that I don't want to put more effort into fourth.
If I was sitting in a chair at Paizo, I'd be looking for a way to hit a death punch on D&D in the next year, probably by stealing away Mearls and Cook. (Unless there was some social or cultural data that suggested that the success of my product line was directly related to the marketing that WoTC was doing or their product in general.)