I have to agree that #300 was a disappointment, but I've felt that way about every issue for the past year or so. In part this is because the magazine seems to focused on marketing the latest products - remember the Annual, which was little more than a collection of marketing pieces for D20 material? This latest issue was far more focused on introducing the BOVD than on celebrating 300 issues of the magazine.
I remember seeing my first Dragon about 25 years ago (issue #3) and being so excited about the article on character backgrounds. Later issues had articles on using weather in a campaign (which I used extensively), on creating believable dungeons ("Let There Be a Method to Your Madness"), on Metamorphosis Alpha (which inspired me to send the players through a dungeon with robots), and so on. The artwork in the very early Dragons did not compare with what we see today, but the focus seemed so much better.
IMHO, I'd suggest two directions for the Dragon for the future:
1. Focus on material which can be used by all (nearly all) GM's and players. I don't mind FR stuff, as long as I can adapt it without too much trouble. Articles that require me to go out and buy yet another $30 book before I can use the material from the article should be used sparingly, if at all. Let WOTC put that stuff on their website. Some of the best material the Dragon ever published was the series of articles on Dungeoncraft by Ray Winninger - we need more quality articles like his. For 3E, Class Acts was great - what about doing a series on how to shape the various classes and characters, without resorting to prestige classes, e.g, the fighter as archer, tank, leader, etc; the wizard as sage, explorer, scientist, and so on?
2. Give me something new! I love the drow as villains, but I really expected a new grand villain for the new edition. Since WOTC hasn't come up with one, why doesn't the Dragon? How about physically weak shapeshifters who manipulate worlds behind the scenes (not dopplegangers)? Plane traveling villains who scout for an army which conquers entire planes? If not villains, try something else - what about a series on demi-planes? I realize that in 300 issues, the Dragon has seemingly covered it all, but I just don't believe that. There is new stuff (of varying quality) on the web all the time - let's get more of it (the best stuff) in the Dragon.
I've enjoyed the Dragon - off and on - for over 25 years. I really want to continue doing so.