Look, I AGREE with Gygax. He isn't saying that the OGL is destroying D&D. All he said is that he doesn't think it is a good idea to allow people to write books for your game without any control on what they put out because people could associate their book with your game.
I agree with him. I like D&D to be a UNIFIED game. I like to know that the game mechanics make sense and are internally consistant. I'd like to think that someone who likely has read through all the other D&D books and who has a good sense of the D&D vision has at least looked at the book before it got printed. D&D does have its own sense of what fits and what doesn't along with a game balance that (for the most part) it stays pretty close to.
I can't count the number of times that I've talked to gamers at a convention or at my local gaming store or even people who join my group who tell me stories about characters who were this race that gave pluses to all their stats for no level adjustment, who took feats from 3 different publishers D20 system books that let them add their strength, dex, and con to their damage, and their AC, and had a 2-20 crit range (ok, it's a bit of an exaggeration, but it's pretty bad)
With no control over what gets put out, gamers everywhere are integrating D20 system products into their games, and D&D isn't one game anymore, it is now 30 or 40 games that play completely different depending on which D20 system books you are playing with. I like being able to sit down at a table and make a character without having to spend the next 2 or 3 hours listening to the DM tell me all the rules he is adding to the game from D20 system books.
I'll admit one thing, that the OGL HAS made more people play, but that's because they aren't actually playing D&D. I'm with Gygax, if you are playing with house rules, you may be playing a game, but it isn't D&D. Same thing with 3rd party OGL products. Don't get me wrong, some of them may even be BETTER games than D&D, but they aren't D&D. Each person is able to turn D&D into the game they'd actually LIKE to play, so they buy the core books, so they have a basis to begin with. Which does make WOTC more money. However, the problem with that is...I LIKE D&D. It's fustrating when I create a D&D character for a game and I'm told by the DM that it isn't legal.
I, for one, wish that it was the "default" to use the rules as written, without any extra OGL books to confuse things.